Approximately 445 million years ago there was a late Ordovician period, as a result of which approximately 85% of marine species disappeared
The authors of the new work decided to test this theory:they changed the iodine concentration in carbonate rocks of that period. The fact is that iodine served as an indicator of changes in oxygen levels in the ocean in the history of the Earth.
Next, they carried out computer simulationsto visualize past events. It turned out that the extinction was not associated with anoxia in shallow areas of the ocean, in other words, with a lack of oxygen. At the same time, oxygen deficiency was traced in deep-sea regions.
The authors note that anoxia is usuallya consequence of global warming caused by a volcanic eruption. However, at this time, global cooling was occurring on Earth, which cannot be explained by the classical model of oxygen changes in the World Ocean.
According to the researchers, they believe thatThe cause of deep-sea anoxia could be a change in seawater circulation. Therefore, the flow of water saturated with oxygen, which came from shallow seas to deeper zones, will stop.
Based on the results of the work, the scientists stated thatAnoxia is not the only cause of the Ordovician extinction. They also provided new evidence that temperature change is a key mechanism behind environmental disaster.
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