Oxygen rocks: Unique Ontario limestone formation may hold clues to history of Earth's atmosphere

The international, $3-million research project to determine when oxygen first entered the Earth's atmosphere is "like a detective story", says Philip Fralick, a geology professor at Lakehead University in Thunder Bay, Ont.

"There's no witnesses that we can ask so we have to go look at the rocks, and the rocks give us the clues as to what was happening there when those rocks were being formed on the bottom of the ocean," he said.

• LU researcher part of team receiving $2.7M to study history of Earth's oxygen

Fralick and Stefan Lalonde of the European Institute for Marine Studies in Brest, France are studying arock formation, which is nearly three-billion years old, near Red Lake, over 550 kilometres northwest of Thunder Bay.

"It's really, really interesting" said Fralick of the ancient and rare limestone outcropping.

"It's the only place we know of on Earth that has a thick sequence of limestone rocks that are that old. There's older limestone on Earth, but it's just a metre or two thick, whereas at Red Lake, it's 200-metres thick."

The depth is significant because it gives the the team more opportunities to find stromatolites - fossilized structures which hint at the presence of bacteria or other organisms that discharged oxygen as a byproduct of photosynthesis.

"Life was waiting for the presence of oxygen to take the next evolutionary jump," said Fralick, explaining that complex organisms needed it to grow "and we could start on the path towards multi-cellular life, not just bacteria on Earth."

The project is receiving some help from mining company Goldcorp, which is donating three-kilometres of drilled core samples from the rock formation, he said.

Those samples, and others collected in the Red Lake area will be examined centimetre by centimetre, and the most promising ones sent to France for chemical analysis.