Scientists Uncover Ancient Australian Landscapes Through Cosmic Clocks in Zircon Crystals
Scientists have discovered a 'cosmic clock' within tiny zircon crystals, offering a unique insight into the formation and erosion of Australia's landscapes over millions of years. This cosmic clock is a result of the constant bombardment of Earth by cosmic rays, which create isotopes in surface rocks. The key to this discovery lies in the stable noble gas, krypton, which accumulates in zircon crystals over time.
The research team, based in southern Australia, drilled cores from the Nullarbor Plain to collect beach sands rich in Zircon. They then used a laser to vaporize the crystals and measure the krypton released. The amount of krypton in the crystals provided a direct indication of how long the grains had spent on the surface.
A Stable Ancient Landscape
Approximately 40 million years ago, the landscape in southern Australia underwent a very slow transformation. Erosion rates were remarkably low, at less than one meter per million years, similar to the rates in the driest deserts today. The beach sands, rich in Zircon, took around 1.6 million years to migrate from their source to the coast, where they were eventually buried.
During this prolonged erosion process, simpler minerals were gradually stripped away, leaving only the most resilient grains. High sea levels and a relatively tectonically quiet Earth contributed to the low erosion rates, allowing sediments to accumulate over millions of years. As Milo Barham, a Curtin geoscientist, explains, this 'natural filtering' process results in a concentration of hard minerals, which is why Australia's beaches are so abundant in Zircon and other heavy minerals.
Further Exploration
This discovery not only sheds light on Australia's ancient landscapes but also opens up new avenues for research. The cosmic clock within Zircon crystals provides a powerful tool for understanding the geological history of the region, offering insights that could have implications for various fields, including environmental science and archaeology.
