* Astronomy

Blobrana · L

RE: Grand Canyon

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More Evidence for an Ancient Grand Canyon

For over 150 years, geologists have debated how and when one of the most dramatic features on our planet - the Grand Canyon - was formed. New data unearthed by researchers at the California Institute of Technology (Caltech) builds support for the idea that conventional models, which say the enormous ravine is 5 to 6 million years old, are way off.
In fact, the Caltech research points to a Grand Canyon that is many millions of years older than previously thought, says Kenneth A. Farley, Keck Foundation Professor of Geochemistry at Caltech and coauthor of the study.
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New fossil findings discovered by scientists at UC Santa Barbara challenge prevailing views about the effects of "Snowball Earth" glaciations on life, according to an article in the June issue of the journal Nature Geoscience.
By analysing microfossils in rocks from the bottom of the Grand Canyon, the authors have challenged the view that has been generally assumed to be correct for the widespread die-off of early life on Earth.
"Snowball Earth" is the popular term for glaciations that occurred between approximately 726 and 635 million years ago and are hypothesised to have entombed the planet in ice, explained co-author Susannah Porter, assistant professor of earth science at UCSB. It has long been noted that these glaciations are associated with a big drop in the fossil diversity, suggesting a mass die-off at this time, perhaps due to the severity of the glaciations. However, the authors of the study found evidence suggesting that this drop in diversity occurred some 16 million or more years before the glaciations. And, they offer an alternative reason for the drop.
A location called the Chuar Group in the Grand Canyon serves as "one of the premier archives of mid-Neoproterozoic time," according to the article. This time period, before Snowball Earth, is preserved as a sort of "snapshot" in the canyon walls.

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Although financial analysts may cringe when you mention the year 2008, Grand Canyon geologists can smile wide - it was a banner year for geologic research regarding how and when the canyon may have formed. No less than ten new research papers were generated by a host of workers, who saw evidence ranging from a canyon that suddenly "appeared" on the landscape 5 to 6 million years ago, to that which advocates for a canyon that was cut in the same location (but into Mesozoic-age rocks now completely gone) over 50 million years earlier. You've got to love a landform as world famous as this, that can stump the experts and whose age cannot be resolved any clearer than by a factor of 10! The list of these papers was compiled by my colleague Carol Hill of Albuquerque who had a big hand in stimulating so much discussion of the topic.

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Geologists Phil Pearthree and Jon Spencer from AZGS, and Jim Faulds and Kyle House from the Nevada Bureau of Mines are challenging a recent report that claimed the Grand Canyon started forming 17 million years ago.

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New geological evidence indicates the Grand Canyon may be so old that dinosaurs once lumbered along its rim, according to a study by researchers from the University of Colorado at Boulder and the California Institute of Technology.
The team used a technique known as radiometric dating to show the Grand Canyon may have formed more than 55 million years ago, pushing back its assumed origins by 40 million to 50 million years. The researchers gathered evidence from rocks in the canyon and on surrounding plateaus that were deposited near sea level several hundred million years ago before the region uplifted and eroded to form the canyon.

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