The great extinction may have been driven in the midst of the massive expansion of life on Earth Tectonic plates.
New research has found links between rock layers in Antarctica and southern Australia, which at the time were part of the supercontinent Gondwana. This suggests that similar dynamics were occurring around it Great continent Roughly 513 million years ago: Mountains were rising, ancient coral reefs were dying, and material eroding from the continent was flowing into the sea. The study leader said that these moments in time coincide with the extinction known as the Sinec event Paul Miroa sedimentologist at Colorado College.
“It's strange that tectonics is what caused the extinction,” Miro told Live Science.
The Senescian Event occurred during the Cambrian Period (540 million to 485 million years ago), which witnessed a great diversification of life on Earth. Land Known for Cambrian explosion.
But in the midst of this boom, the Siniscus extinction wiped out several key groups, including cone-shelled animals called heliotes and sponges called archaeocytids, which once built enormous coral reefs around the world. Researchers know that the Sinec event was linked to a drop in oxygen levels in the oceans, but they have been unable to pinpoint the exact cause.
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Now, Mairo and his colleagues say they have the answer. The Gondwana tectonics, which formed between 600 million and 540 million years ago, triggered a series of events that sank relict coral reefs and changed the oceans, they reported March 29 in the journal. Advancement of science.
Evidence of these events has been found in rock layers in the Trans-Antarctic Mountains of Antarctica and on Kangaroo Island, Australia. Mairo and his colleagues collected specimens in Antarctica in 2011, including trilobite fossils from ancient, long-dead corals. Then, about a year ago, a geologist at Pomona College Robert Gaines He told Mero he had seen similar rocks on Kangaroo Island, also full of trilobite fossils.
These trilobites were key to the timing of coral loss. Because trilobites evolved so quickly, researchers can tell the age of a rock by the types of trilobites fossilized within it. In both Antarctica and Australia, fossils date back to between 514 million and 512 million years ago, around the time of the Sinec event.
“Everything just clicked into place,” Miro said. “There was the same geological history all the way down in Australia as there was in Antarctica.”
At the time of the Sinisk event, both continents were part of Gondwana, with today's Antarctica on the equator and Australia at a higher latitude. The sites showed a similar story in the rock layers. The extinction of relict corals coincided with giant mountain-building events. As mountains appeared on land, the nearby shallow oceans off the coast subsided in a kind of oscillating crustal motion. This caused the relic reef to suddenly deepen, submerging it beyond its ability to survive. Then, erosion from the new mountain ranges dumped layers of pebbles and pebbles over the sunken reefs.
Meanwhile, tectonic movements that caused mountains to rise in some places also caused the Earth's crust to expand in other places, allowing magma to rise to the surface and solidify into basalt rock, a geological formation known as the “Great Igneous Province,” Miro said. “This hot magma brought a lot of… Greenhouse gasessuch as sulfur dioxide and carbon dioxide, causing the temperature of the Earth's atmosphere to rise.
This warming, in turn, has slowed ocean circulation, a phenomenon that worries researchers It may happen again today With human-caused Climate change. This slowdown in ocean circulation caused oxygen-rich water to sink to the ocean floor. This killed many existing organisms, Miro said.
“The older, more primitive ones didn’t do as well,” he said.
Large igneous provinces have been blamed for other extinctions, but with less certainty than the Sinske event. “I don't know of any other regions that I can point to where they have been clearly identified,” Miro said.
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