There was more than simple oxygen depletion to ancient mass extinction event
Thallium isotopes reveal that rapid swings in ocean oxygenation preceded the events that wiped out 90% of species 250 million years ago
Research on thallium isotope ratios suggests that the true reason up to 90% of the Earth’s species died out around 250 million years ago may be fluctuations in the oceans’ oxygen levels rather than a simple drop in dissolved oxygen.
Sediment records have suggested that the end-Permian mass extinction – the largest mass extinction in Earth’s history – resulted from a cascade of detrimental environmental effects triggered by increased volcanism, leading ultimately to extreme global heating and oceanic anoxia. However, new research has found that, just prior to the extinction, ocean oxygen levels actually increased.