Scientists have discovered fossilized mega-ripples in Louisiana, supporting the theory of a giant space rock hitting the sea near Mexico’s Yucatan Peninsula 66 million years ago that caused a mile-high tsunami.
For the past several decades, scientists have theorized that an asteroid struck the water near Mexico’s southeastern coast, kicking up a blanket of dust that blotted out the sun for a long period of time, reducing temperatures and ultimately killing off the dinosaurs.
A tsunami in the Gulf of Mexico was generated by the event, known as the Chicxulub impact, that some experts believe was up to nearly a mile in height. The tsunami crashed into North America and was followed by smaller waves.
Scientists now believe they have discovered evidence of the event in what is central Louisiana today.
“It is great to actually have evidence of something that has been theorized for a really long time,” said Sean Gulick, a geophysicist at the University of Texas.
To find ancient structures underground, scientists use industrial hammers or set off explosives in the earth and use seismic imaging to look for reflections from the many layers of rock and sediment below. Companies use the same technique to look for gas and oil, revealing a great deal of data for scientists to use as research, especially in regions around the Gulf of Mexico.
Over a decade ago, University of Louisiana geophysicist Gary Kinsland obtained seismic images from the company Devon Energy.
Sea levels were higher at the time of the asteroid collision, and Kinsland believed the area held clues as to what happened in the shallow waters off the coast.
Kinsland and colleagues saw fossilized ripples when analyzing a layer about 1,500 meters (just under a mile) under the earth. The mega-ripples were spaced up to a little over a half-mile apart with an average height of about 3 feet.
Scientists believe the ripples are the imprint of the tsunami’s waves as they approached the coast in water around 197 feet deep, disturbing sediments on the seabed.
Kinsland said the orientation of the mega-ripples was also consistent with the Chicxulub impact.
He said the location was ideal for preserving the ripples: “The water was so deep that once the tsunami had quit, regular storm waves couldn’t disturb what was down there.”
The Chicxulub impact was first hypothesized in the 1980s. Cores from a drilling expedition in 2016 revealed details about how the impact crater was formed.
Then, in 2019, researchers in North Dakota (about 1,900 miles north of Chicxulub), discovered a fossil site that they said records the hours after the impact and includes debris dragged inland from the tsunami.
“We have small pieces of the puzzle that keep getting added in,” said Alfio Alessandro Chiarenza, a paleontologist at the University of Vigo.
“Now this research is another one, giving more evidence of a cataclysmic tsunami that probably inundated [everything] for thousands of miles.”
(Edited by Judith Isacoff and Matthew B. Hall)
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