A small black rock brought back by a student from a study trip through the Western Australian outback has been broken open to reveal the remains of 2.4 billion-year-old creatures.
The remarkable thing about these microfossils is that they appear to be more complex than anything that existed at the time. Not just a few years, but 750 million.
They appear to belong to a domain of complex life called eukaryotes — a domain that includes animals, plants, and fungi. Previously, it was thought that only single-celled bacteria-like life forms called prokaryotes existed.
Although the texture of the fossils is extremely good, the chemical information is degraded, making proving the hypothesis difficult. But given the random series of events that led to the discovery, the researchers are determined to continue studying this mysterious find.
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Chance event leads to discovery of microfossils in rocks
The layered limestone rock, known as black flint, was found by geologist Dr Erica Barlow in the Pilbara and taken home as a souvenir. She was pursuing another line of research as a student at the University of NSW when her supervisor Professor Martin Van Kranendonk spotted it on her desk.
“The particular type of rock that Erica had on her desk is known to contain samples of microfossils,” Van Kranendonk told Yahoo News. “I had seen a number of those types of rocks, but this particular sample looked extraordinarily glassy.”
Although the pair studied in a geology lab, the chances were slim that anyone would know the significance of the black flint. Perhaps a few dozen people around the world would recognize it.
The chance of finding the stone was also small. “It was literally a needle in a haystack,” Van Kranendonk said.
Ancient landscape where microfossils have been discovered
To reach the remote town of Pilbara in Western Australia, you have to travel a long, bumpy dirt road.
“It’s terribly hot in the summer. But it’s a 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 wide open valleys filled with gum trees along the river. And then these dark red mountain ranges with all the iron. It’s spectacular.”
Why the rock is so important
The dating of the rocks is important because this is the period during which the Great Oxidation Event occurred, a turning point marking the rise of oxygen in the atmosphere of the early Earth.
Theoretically, the event was linked to a leap in the complexity of life, but physical evidence was lacking.
When the researchers looked at the fossils inside, they didn’t look like anything they had seen before. It’s the first fossil of its kind known in the geological record.
Since the original discovery of the rock, Barlow has returned to the site and found an entire rock face embedded in black flint for miles. Several small pieces have been removed and returned to the lab for further study.
Van Kranendonk hopes that the technology will develop further and that a more definitive analysis of the microfossils can be made, so that it can be determined whether the creatures living in them are eukaryotes.
During this research project, Van Kranendonk was a professor at the University of NSW. He is now the new Head of the School of Earth and Planetary Sciences at Curtin University in the Faculty of Science and Engineering.
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