An international group of scientists has determined the mechanism of one of the largest mass extinction on Earth, which occurred in the late Ordovic period about 445 million years ago. Then approximately 85 percent of the types of marine organisms who lived in the shallow water zone of oceans disappeared near the continents. Article researchers published in the journal Nature Geoscience.
According to one of the hypotheses, the extinction could occur due to lack of oxygen in sea water. To check this version, the scientists measured the concentration of iodine in the carbonate rocks of that period. The iodine serves as an indicator of changes in the oxygen level in the ocean in the history of the Earth. In combination with computer modeling, the data showed that there was no evidence that the extinction is somehow connected with anoxy in shallow ocean areas. At the same time, the oxygen deficit was traced in deep-sea regions.
Usually anoxia is associated with global warming caused by the eruption of the volcano. However, at this time there was a global cooling on Earth, which cannot be explained by the classic model of oxygen changes in the World Ocean. Scientists suggest that the cause of deep-sea conversion can be a change in the circulation of sea water, as a result of which the flow of oxygen-rich water from the shallow seas in deeper zones was stopped.
Research results exclude an ignion as the only explanation of the Ordovicary extinction and provide new data in favor of the fact that the temperature change is the key mechanism of the environmental catastrophe.