Pratt and Sproat visited three sites north of Pass, Man., where they found evidence of short-lived, high-energy events in this ancient ocean that geologists had previously not noticed.
Certain layers of sediment at the site had been torn apart into pebbles and mixed with clay. The floor beneath the deeper waters of the basin did not contain clay, so it could only have come from land.
Professor Platt, from the School of Geological Sciences, said: “We realized we needed an event where we would tear up the ocean floor and somehow bring all this clay back, so we did that several times.”
I can’t think of any answer other than a tsunami.
There were few animals or plants on land to witness that day nearly 500 million years ago, but if observers had been nearby, they would have witnessed a dramatic event.
Faults in the Earth’s crust in this region have been quiet for thousands of years now, but they were still active back then. One of these faults, somewhere in the northern half of the Williston Basin, suddenly slipped, sending a violent shock wave into the ocean.
The water level on the coast would have dropped temporarily, then rose inexorably. The waves may have traveled more than a kilometer (1 kilometer) along the gentle slope, scouring the rocky surface. When it finally retreated, the clay was pushed back into the sea. More waves followed.
While Pratt acknowledged that tsunami was a “radical interpretation” of the evidence, the USask researchers had an advantage. The geological formations of Canada’s Williston Basin are almost completely hidden beneath the flat topography of Manitoba and Saskatchewan, and to date geologists have discovered only a few natural outcrops, core samples, and road cuts. limited to research.
Over the past decade, several new quarries have been dug in northern Manitoba, revealing more of the basin’s secrets.
“What opened our eyes was touring the quarries. When you go into these quarries, you can see the layers extending over 100 meters horizontally, and the same layer can be found in multiple locations. And it gave us a 3D perspective that no one had before,” Pratt said.
Similar deposits can also be caused by large storms, but Sproat and Platt said they didn’t think storms could be the culprit, since there are no other clear signs of regular storm activity. Eliminated. Additionally, the region was too close to the ancient equator to experience hurricanes.