Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Amazon River reversed flow

26.10.2006
Ask any South American dinosaur which way the Amazon River flows and she would have told you east-to-west, the opposite of today. That's the surprising conclusion of researchers studying ancient mineral grains buried in the Amazon Basin.

The once westward roll of what is now the world's largest river was caused by a long-gone highland near what today is the river's mouth. That highland was created by the breaking away of South America from Africa and the creation of the Atlantic Ocean during the Cretaceous Period, 65 to 145 million years ago. Later, when the Andes rose up on the western side of South America, the river had no choice but to drain into the new ocean.

"It just happened in a way that the current Amazon could take advantage of where an old river and ocean basin used to sit," said geologist Russell Mapes, a doctoral candidate at the University of North Carolina in Chapel Hill.

Previous Brazilian and U.S. researchers have proposed smaller scale reversals and splits in the Amazon Basin, but nothing on the scale of the entire basin, said Mapes.

The evidence for the Amazon's ancient switcheroo comes in the form of tiny crystals of a mineral called zircon, as well as telltale signs of the river flow direction captured in the structure of old river sediments.

Zircons are stubbornly long-lived and tend to be recycled over and over without stopping their internal uranium-lead radioisotope clocks that started ticking when the minerals first formed. As a result, they are tiny windows for peaking at long-lost mountains and entire continents.

The zircons in old sands studied by Mapes, his UNC faculty advisor Drew Coleman, and their Brazilian colleagues Afonso Nogueira and Angela Maria Leguizamon Vega, stand out because they do not appear to come from the Andes at all. In fact they date to about 1.3 to 2.1 billion years ago. So they had to have been formed in rocks that solidified in mountains that eroded away into the earliest Amazon.

Mapes is scheduled to present the team's findings on Wednesday, 25 October, at the Annual Meeting of the Geological Society of America in Philadelphia. What he won't have time to describe to other researchers is the adventure they underwent to gather up those little zircons.

"It was a pretty exotic trip," said Coleman. "We took planes and aluminum small boats. In the first year we took a two-and-a-half week cruise up the river from Manaus. We sampled young and old sediment outcrops on the river. We traveled about 500 kilometers."

"In the second year, we did three small hops -- plane flights downstream then rented small boats at each stopping point," recalls Mapes. "One night in a boat we ran out of gas in an electrical storm. Luckily, it was the one place in the basin where my cell phone worked. We called the man who rented the boat to us and he came out and got us. We just bobbed around. It was a place where the river is several miles wide."

In the end, said Mapes, it was worth it to finally be able to see back further in time. "When I got the actual data back, I was happy."

WHEN & WHERE

EVIDENCE FOR A CONTINENT SCALE DRAINAGE INVERSION IN THE AMAZON BASIN SINCE THE LATE CRETACEOUS 2:00-2:15 p.m., Wednesday, 25 October 2006 Pennsylvania Convention Center Room 112 A

Ann Cairns | EurekAlert!
Further information:
http://www.geosociety.org
http://gsa.confex.com/gsa/2006AM/finalprogram/abstract_113025.htm

More articles from Earth Sciences:

nachricht Impacts of mass coral die-off on Indian Ocean reefs revealed
21.02.2017 | University of Exeter

nachricht How much biomass grows in the savannah?
16.02.2017 | Friedrich-Schiller-Universität Jena

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Microhotplates for a smart gas sensor

22.02.2017 | Power and Electrical Engineering

Scientists unlock ability to generate new sensory hair cells

22.02.2017 | Life Sciences

Prediction: More gas-giants will be found orbiting Sun-like stars

22.02.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>