Small rock found in outback reveals 2.4-billion-year-old mystery

When they looked at the rock under a microscope the creatures fossilised inside were like nothing else researchers had seen.

Dr Erica Barlow at a campsite in 2013 on the Pilbara.
Dr Erica Barlow found her piece of black chert during a research trip in 2013. Source: UNSW

A small black rock souvenired by a student during an outback study trip in Western Australia has been cracked open to reveal the remains of 2.4-billion-year-old creatures inside.

What’s remarkable about these microfossils is they appear to be more intricate than anything known to exist at the time. Not just by a few years, but by 750 million.

They appear to belong to a domain of complex life called eukaryotes — a domain that includes animals, plants and fungi. It had previously been thought all that existed was single-celled bacteria-like life called prokaryotes.

While the texture of the fossils is extremely good, the chemical information has been degraded and that makes proving the hypothesis difficult. But given the random series of events that led to the find, the researchers are committed to keep studying this mysterious find.

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A black and white microscope picture of the creature inside a rock.
Looking through a microscope at the rock, the researchers discovered a creature that appeared to be multi-celled. Source: UNSW

The layered limestone rock, known as a black chert, was found by geologist Dr Erica Barlow in the Pilbara and taken home as a keepsake. She’d been pursuing a different line of research as a student at University of NSW before her supervisor Professor Martin Van Kranendonk spotted it on her desk.

“The particular type of rock that Erica had on her desk is well known to contain samples of microfossils,” Van Kranendonk told Yahoo News. “I'd seen some of those types of rocks, but this particular sample looked extraordinarily glassy.”

Although the pair were studying in a geology lab, the chances of anyone knowing the significance of the black chert were low. Maybe a couple of dozen people throughout the world would recognise it.

The odds of discovering the rock were also slim. “It was literally a needle in a haystack,” Van Kranendonk said.

Inset - a piece of black chert. Background - the Pilbara landscape where the rock was discovered in 2013
Several pieces of black chert have now been retrieved from the Pilbara. Source: UNSW

To get to the remote Western Australian Pilbara town where it was located requires travelling down a long and bumpy dirt road.

“It’s fiercely hot in the summer. But it’s beautiful wilderness — it's still a very pristine part of the world in the southern part of the Hamersley Ranges,” Van Kranendonk said.

“There are broad open valleys that are filled by gum trees along the river course. And then these dark red ranges with all the iron. It's spectacular.”

The period the rock was dated to is significant because it’s when the Great Oxidation Event occurred — a tipping-point that marks the rise of oxygen in the early Earth's atmosphere.

Dr Erica Barlow in a dark blue jumper looking at slide containing her rock.
Dr Erica Barlow thinks the creatures inside her rock could rewrite our understanding of life on Earth. Source: UNSW

The event had theoretically been linked to a jump in the complexity of life but physical evidence had been lacking.

When the researchers looked at the fossils inside they didn’t resemble anything they’d seen before. It’s the first fossil of its kind known to the geological record.

Since the original discovery of the rock, Barlow has returned to the site and found an entire rock wall embedded with black chert for kilometres. Several small pieces have been removed and taken back to the lab for further study.

Van Kranendonk is hopeful that as technology develops, it will become possible to create a more definitive analysis of the microfossils that will enable them to pinpoint whether the creatures inside are eukaryotes.

During this research project Van Kranendonk was a Professor at the University of NSW. He is now the Curtin University’s new Head of School of Earth and Planetary Sciences in the Faculty of Science and Engineering.

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