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In addition to being one of the Seven Natural Wonders of the World, the Grand Canyon is a living history book, revealing great geological eras on its various strata.
Today, researchers in Colorado believe they have unraveled the mystery surrounding a “gap” of more than a billion years in this record, known as “The Great Discord.”
In an article published in the journal Geology, they theorize that the explosion of an ancient supercontinent, known as Rodinia, over 630 million years ago, triggered a series of small but powerful earthquakes. that have driven millennia of rocks and feelings over the canyons. east side in the ocean.
“Over a billion years have passed,” senior author Barra Peak, a geology graduate student at CU Boulder, said in a statement.
“It’s also a billion years during an interesting part of Earth’s history where the planet transitions from an older setting to the modern Earth we know today.”
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Researchers at the University of Colorado believe that the tectonic upheaval caused by the bursting of an ancient supercontinent has distorted the Grand Canyon and created a billion-year “gap” in its geological records.
Rodinia formed around a billion years ago and split between 750 and 633 million years ago, with its fragments reassembling to eventually form Pannotia, a short-lived Pan-African supercontinent.
It is believed that the dissolution of Rodinia cooled the planet and opened the door for the massive and rapid evolution of primitive life in Cambrian times, but little is known about Rodinia’s geological history or even its configuration.
If her breakup is related to the “Great Discord,” it could shed light on both.
“The large unconformity is one of the first well-documented geological features in North America,” lead author Barra Peak said in a statement.
“But until recently, we didn’t have a lot of constraints on when or how it happened.”
A recent photograph of the Grand Canyon from the Walhalla Plateau, with the red line indicating the Great Discordance
The difference in geological strata in the east and west sides of the canyon, known as “the great unconformity”, has caused the billion-year immersion of rocks and feelings.
Self-taught explorer and geologist John Wesley Powell observed the Great Discordance during his historic boat trip on the Colorado River more than 150 years ago in 1869.
By sketching a section of the canyon, he showed how the Middle and Upper Proterozoic rock strata are almost vertical, compared to the horizontal strata above them.
Peak, a geology graduate student at CU Boulder, said the phenomenon made “beautiful lines” visible from the Colorado River.
A drawing of a stratigraphic section of the Grand Canyon by John Wesley Powell from 1875. The area of section ‘B’ between ‘x’ and ‘y’ represents ‘nonconforming’ areas which do not correspond to the direction of other strata
“At the bottom you can see very clearly that there are rocks that have been pushed together,” she said in the statement.
“Their layers are vertical. Then there is a cutoff, and on top of that you have these beautiful horizontal layers that form the mounds and peaks that you associate with the Grand Canyon.
His team used “thermochronology,” which tracks the history of heat in rock left by pressure from geological formations buried deep underground.
“We have new analytical methods in our lab that allow us to decipher history in the missing window of time through the Great Discord,” co-author Rebecca Flowers, professor of geological sciences at CU, said in the release. .
By sampling rocks from all over the canyon, they found that the western and eastern parts had different heat histories and likely underwent different geological changes over time.
“It’s not a single block with the same temperature history,” Peak said.
Judging by the heat levels, the basement rock in the west rose to the surface around 700 million years ago, while the equivalent rock was submerged under miles of sediment.
The big difference was caused by the break-up of Rodinia, Peak said, with earthquakes and “faulty events” contorting the earth in different ways – and creating the Great Discord.
She and her colleagues are now looking to explore similar periods of wasted time at sites in North America.
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