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 By saving cost and energy, the lighting revolution may increase light pollution
23.11.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

nachricht Frictional Heat Powers Hydrothermal Activity on Enceladus
23.11.2017 | Universität Heidelberg

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Underwater acoustic localization of marine mammals and vehicles

23.11.2017 | Information Technology

Enhancing the quantum sensing capabilities of diamond

23.11.2017 | Physics and Astronomy

Meadows beat out shrubs when it comes to storing carbon

23.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>