A piece of Canada that broke off about 1.7 billion years ago has been found in Australia.

Geologists analyzed chemical signatures for very ancient sedimentary rocks in Georgetown, Queensland, that offer clues about where those rocks were when they formed.

At that time, the continents were drifting together to form a supercontinent called Nuna or Columbia. The data suggests that the Georgetown rocks broke off from Canada and collided with northern Australia around 1.6 billion years ago. It remained there even after Nuna broke apart 300 million years later.

The researchers found a geological signature that "cannot be linked with any other rocks in Australia," Adam Nordsvan, lead author of the new research, said in an email to CBC News.

Instead, it's "strikingly similar to other sedimentary rocks deposited at a similar time in North America, in particular the Wernecke Supergroup of the Yukon region and the Athabasca Basin."

This cartoon illustrates how the Georgetown terrane of present-day northern Queensland was originally part of North America some 1,700 million years ago. It then joined Australia at around 1,600 million years ago during the formation of the supercontinent Nuna, and has remained part of Australia since. (Adam Nordsvan/Curtin University)

Throughout Earth's history, the continents drifted together and apart numerous times. They most recently formed the supercontinent Pangea 300 million years ago before breaking up to form today's continents.

That makes it difficult to figure out how previous supercontinents were configured, or even exactly when they formed.

Nordsvan, a doctoral researcher at Curtin University in southwestern Australia, said there was some debate about whether northeastern Australia was connected to North America or to Siberia when Nuna formed.

"Our data rules out the Siberia option," he told CBC News.

The study was led by Adam Nordsvan, left, a PhD student at Curtin Univesity in Western Australia. He is pictured here studying the 'North-American sourced' sediments in Georgetown, Australia, with co-author Ian Withnall of the Geological Survey of Queensland. (Amaury Pourteau)

The new study, published earlier in January in the journal Geology, also supports other evidence that Nuna formed about 1.6 billion years ago.

The study was funded by the Australian Research Council and Curtin University in Western Australia.

Economic implications

David Schneider, a professor of earth and environmental sciences at the University of Ottawa who was not involved in the research, said the study was well done.

"This is pretty good evidence that that part of Australia was probably attached to Canada at some point," said Schnieder, who investigates the timing and rates of different processes and events involving the Earth's tectonic plates.

He noted that the findings could have economic implications. There are gold deposits near Georgetown — meaning it would be worth exploring for gold in the Yukon where it could have been attached.

Current ripple laminations in fine to medium grained sandstone sedimentary rocks in Georgetown indicate ancient shallow marine environments. The new study found the sediments were deposited off the coast of North America adjacent to present-day Canada and later transferred to Australia. (Adam Nordsvan/Curtin University)

The technique that Nordsvan and his team used to figure out the origin of the Georgetown rocks involves looking for grains of a mineral called zircon. Zircon often contains radioactive uranium, which decays to lead over time. The ratio of lead to uranium indicates when the zircon formed, with older rocks containing a higher ratio of lead to uranium than younger rocks.

The zircon itself forms from magma, either from volcanoes or from underground, so its age provides a record of events involving magma in the local area near where the zircon is deposited — a signature of sorts.

However, Schneider said it's not the only technique used to confirm the age and origin of rocks. More evidence will be needed to link the Georgetown rocks to Canada with more certainty.