uOttawa News

OTTAWA, November 20, 2014  —  444 million years ago during the end of the Ordovician period, 85% of marine life became extinct. For the past 20 or 30 years, one theory has explained this extinction: a single glacial period. Now, a team of researchers including André Desrochers of the University of Ottawa has debunked this theory in findings published in Nature Communications. By combining two of the period’s most important archives, from Morocco and Anticosti Island, the international team was able to determine that in fact multiple glaciations were the cause of marine life extinction.

“During the end-Ordovician period, Morocco was at the South Pole and Anticosti Island was located near the equator, making for two very different geological contexts,” says Desrochers, director and associate professor, Department of Earth Sciences. “With Morocco closer to the glaciation, they have the most important records from that period. Anticosti, on the other hand, has the most important fossil records.”

The research teams’ combined archives were able to show that every glaciation in Morocco caused a lower ocean level in Anticosti. With this knowledge, they were able to demonstrate that there was not only one glaciation that caused marine extinction, but several over a short period of time.”

While a team in France led by Jean-François Ghienne of the Université de Strasbourg worked with archives in Morocco and analyzed unique glacial and periglacial sedimentary rocks to decipher major climate changes at the end of the Ordovician period, Desrochers’ team sought to understand the Earth’s fossil records, particularly those of Anticosti Island, an exceptional geosite recognized worldwide for its abundance of 440 to 450 million year-old fossils.

“Anticosti is a natural world heritage treasure. It has over 600 km of coastline. The geological archives on the island are better exposed, more fossiliferous and more complete than any other place on earth,” says Desrochers.

Will Anticosti Island answer more questions about the end of the Ordovician period? Stay tuned.

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