Scanning electron microscope image of zircon crystals. Each crystal is about 0.1 millimeters in size, which is roughly the thickness of a human hair, and records cosmogenic krypton as a geochemical time archive.
Photo Credit: Maximilian Dröllner
Scientific Frontline: "At a Glance" Summary
- Main Discovery: A new geochronological method utilizing cosmogenic krypton isotopes trapped in zircon crystals has been established to reconstruct the erosion and exposure history of ancient Australian landscapes.
- Methodology: Researchers analyzed krypton gas generated by cosmic ray interactions with zircon grains to quantify the duration these minerals spent near Earth's surface prior to burial, effectively functioning as a "cosmic clock."
- Geological Insight: The data indicates that during periods of tectonic stability and high sea levels, erosion rates slow dramatically, causing sediments to be stored and reworked near the surface for millions of years.
- Resource Formation: This prolonged surface exposure facilitates the weathering of unstable materials while concentrating durable minerals, explaining the geological origin of Australia's extensive mineral sand deposits.
- Significance: The findings provide a long-term perspective on how landscapes respond to deep-seated tectonic and climatic forces, offering critical data to improve predictive models for future land management and sediment system changes.
Curtin University researchers have demonstrated a new way to uncover the ancient history of Australia’s landscapes, which could offer crucial insights into how our environment responds to geological processes and climate change and even where deposits of valuable minerals may be found.
The international team led by Curtin’s Timescales of Mineral Systems Group at the School of Earth and Planetary Sciences, in cooperation with the University of Göttingen and the University of Cologne, studied tiny crystals of zircon found in ancient beach sands.
Zircon is one of the toughest minerals on Earth and can survive weathering, erosion and long journeys through rivers and coastlines over millions of years.
Trapped inside zircon grains is a rare gas called krypton, which is created when minerals are exposed at Earth’s surface and hit by cosmic rays (high-energy, charged subatomic particles from space).
By measuring the krypton, the team was able to work out how long zircon grains spent near the Earth’s surface before they were buried, like a ‘cosmic clock’ offering a window into the past to see how quickly or slowly the ancient landscape eroded and shifted over vast periods of time.
Lead author and Adjunct Curtin Research Fellow Dr Maximilian Dröllner, also from the University of Göttingen, said this approach allowed scientists to study landscapes far older than previously possible, which could provide valuable insight into how the Earth’s surface may respond to ongoing climate and tectonic change.
“Our planet’s history shows climate and tectonic forces can control how landscapes behave over very long timescales,” Dr Dröllner said.
“This research helps us understand what happens when sea levels change and how deep-seated Earth movements influence the evolution of landscapes.”
The findings show when landscapes are tectonically stable and sea levels remain high, erosion slows dramatically and sediments can remain stored and reworked near the surface for millions of years.
Co-author and Timescales of Mineral Systems Group lead Professor Chris Kirkland, said this has relevance for understanding the evolution of the surface of the planet over billions of years, but also future societal planning and land management.
“As we modify natural systems, we can expect changes in how sediment is stored in river basins and along coastlines and continental shelves,” Professor Kirkland said.
“Our results show that these processes can fundamentally reshape landscapes, not just coastlines, over time.”
Co-author, Associate Professor Milo Barham, also from the Timescales of Mineral Systems Group, said the study also had important implications for Australia’s mineral resources.
“Climate doesn’t just influence ecosystems and weather patterns; it also controls where mineral resources end up and how accessible they become,” Associate Professor Barham said.
“Extended periods of sediment storage allow durable minerals to gradually concentrate while less stable materials break down, explaining why Australia hosts some of the world’s most significant mineral sand deposits.
“Understanding these links is critical as demand for these minerals continues to grow, as it provides a long-term perspective that can improve models used to predict future environmental and resource outcomes arising from changes to these sediment systems.”
Related material: Cosmogenic krypton enables reconstruction of landscapes millions of years old
Published in journal: Proceedings of the National Academy of Sciences
Title: Ancient landscape evolution tracked through cosmogenic krypton in detrital zircon
Authors: Maximilian Dröllner, Milo Barham, Christopher L. Kirkland, Taryn Scharf, Sabrina Niemeyer, and Tibor J. Dunai
Source/Credit: Curtin University | Samuel Jeremic
Reference Number: es011426_01
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