Northwestern Ontario rock formation helps scientists study 'ancient atmosphere'

A  rare rock formation, located about 100 kilometres east of Thunder Bay, Ont., has helped an international group of researchers "sample the ancient atmosphere" to determine the abundance of living things existing on Earth a billion years ago, as compared to the present day.

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

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

Scientists examined the ratio of oxygen isotopes trapped in a mineral called gypsum, which is a key component of drywall building materials, says Philip Fralick, a Lakehead University geology professor, who was part of the collaborative effort.

"This is one of the oldest gypsum deposits on Earth." he said, describing the red rock cliffs, near the communities of Dorion and Nipigon.

'Back to the beginning of Earth itself'

"It's 1.4 billion years old, one-third of the way back to the beginning of Earth itself, so back then there was only very, very primitive life, there was bacteria, there was a few one-cell metazoans and there may have been worms but that was about it."

Gypsum is left behind when oceans and saline lakes dry up.

"If you take a bucket of seawater and put it on your stove, after about two-thirds of the water has evaporated away, gypsum crystals will start to form," he said.

Because of its ability to trap oxygen, gypsum can provide scientists with a snapshot of the atmospheric conditions present during its creation.

'A lot, lot, lot less life on the Earth at the time'

Oxygen is a key component of almost all living things. Plants produce it during photosynthesis. Animals need it to breathe and burn calories.

It occurs as three isotopes, based on the number of neutrons present, and "it's a pretty constant ratio but the ratio can get messed up by photosynthesis," said Fralick.

Measuring the variation in the ratio of oxygen collected from the atmosphere today and over a billion years ago means scientists "can tell if there was more plant life or less plant life".

In fact, "we found that there was a lot, lot, lot less life on the Earth at the time," he said. The finding itself is not surprising, but what is "revolutionary" is the new technique, developed by this international research project, said Fralick.

He expects the procedure will be used in future studies to show the evolution of plant and animal life on Earth.

You can hear the full interview with Prof. Fralick on CBC's Superior Morning here.

The study has been published on Nature.com.