The tiny zircon remnants were discovered in northern Ontario by an international research team led by University of Western Ontario Professor Desmond Moser. Measuring no more than the width of a human hair, the 200-million-year growth span of the ancient microcrystals is longer than any previously discovered.

Moser said the findings provide a new record of planetary evolution and contradict previous experimental predictions the crystals would change when exposed to heat and pressure upon burial in the deep Earth.

"This research shows that these crystals are incredibly resistant to change and proves, for the first time, that the growth zones we see inside them contain an accurate record of their movements through and around the Earth," said Moser.

The research appears in the March issue of the journal Geology.