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Big freeze hit oceans 116 million years ago

A COLD snap that made the dinosaurs shiver 116 million years ago caused a crisis in the oceans similar to the effects of global warming.

The 2.5 million-year cooling period led to the disruption of populations of small plants and animals that form the foundation of marine ecosystems.

For most of the Cretaceous period, which marked the height of the dinosaurs' reign, the Earth was a hothouse, with temperatures about 6C higher than today.

But scientists confirmed that right in the middle of the Cretaceous, average global temperatures plunged by up to 5C.

Analysis of an ocean floor sediment core taken from the north Atlantic showed how the change led to a major shift in the global carbon cycle.

It coincided with the decline of some groups of marine plankton and extinction of surface-dwelling micro-organisms. At the same time, the abundance of certain cold-water organisms increased.

The cause of the cold snap is thought to have been the break-up of the super-continent Pangaea, which opened up new ocean basins around Africa, South America and Europe.

This created additional expanses of water containing green algae and other plant-like organisms that sucked carbon dioxide from the atmosphere.

hnews@herald.ie


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