Approximately 445 million years ago was the late Ordovician period, as a result of which about 85% of marine species disappeared
The authors of the new work decided to test this theory:they changed the concentration of iodine in carbonate rocks of that period. The fact is that iodine served as an indicator of changes in the level of oxygen in the ocean in the history of the Earth.
Then they carried out computer simulations,to visualize the events of the past. It turned out that the extinction was not associated with anoxia in the shallow waters of the ocean, in other words, with a lack of oxygen. At the same time, oxygen deficiency was observed in deep-water regions.
The authors note that anoxia is usuallya consequence of global warming caused by a volcanic eruption. However, at this time, a global cooling took place on the 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 the circulation of seawater. Therefore, the flow of oxygenated water that went from shallow seas to deeper zones will stop.
According to the results of the work, scientists stated that anoxia -this is not the only reason for the Ordovician extinction. They also provided new evidence that temperature change is a key mechanism for environmental disaster.
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