Noble gas laboratory in Cologne where the krypton was analyzed for the study.
Photo Credit: © Dr Tibor Dunai
Scientific Frontline: "At a Glance" Summary
- Geochemical Innovation: Researchers have developed a novel method to reconstruct landscape evolution from tens of millions of years ago by analyzing cosmogenic krypton isotopes trapped within zircon minerals.
- Methodological Framework: The approach integrates measurements of stable cosmogenic krypton—produced by cosmic radiation hitting surface minerals—with traditional U-Pb dating to distinguish between the time of mineral formation and the duration of surface exposure.
- Sediment Residence Times: Analysis of drill cores from Australia's Eucla Basin revealed that some zircon grains remained on the Earth’s surface for over one million years before final deposition.
- Paleoclimate Correlation: Data identifies a transition in the middle Eocene from long-stored, weathered sediments to more dynamic transport systems, a shift that aligns with documented fluctuations in sea levels and tectonic activity.
- Extended Temporal Range: Unlike established cosmogenic nuclides with short half-lives that limit dating to recent geological history, the stability of cosmogenic krypton allows for the quantitative tracking of sediment transport and storage over tens of millions of years.
- Future Application: The technique provides a primary tool for quantifying the landscape history of tectonically stable continents and assessing how ancient climate changes influenced long-term Earth surface dynamics.
An international research team involving the University of Cologne has found a new way to reconstruct how landscapes developed tens of millions of years ago and how long sediments remained on the Earth’s surface before they were deposited. The investigation of cosmogenic krypton in zircon minerals makes it possible for the first time to quantitatively record the transport and retention times of sediments over millions of years. Cosmogenic krypton is a rare noble gas that is produced when cosmic radiation hits minerals on the Earth’s surface. Analyzing these minerals can therefore show how long they were on Earth’s surface. The study titled “Ancient landscape evolution tracked through cosmogenic krypton in detrital zircon” was published Proceedings of the National Academy of Sciences. The researchers show that cosmogenic krypton in certain tiny mineral grains can be used to quantitatively reconstruct landscape development around 40 million years ago.
The study is based on sediment samples from several drill cores in the Eucla Basin in southern Australia, one of the world’s most important zircon deposits. The researchers combined measurements of stable cosmogenic krypton isotopes with the established U-Pb dating of zircons. U-Pb dating is a method that allows researchers to determine when these minerals were formed millions or even billions of years ago based on the natural decay of uranium to lead in resistant minerals such as zircon. While the U-Pb ages mainly provide information about the origin of the mineral grains, the cosmogenic krypton allows conclusions to be drawn about how long these minerals were exposed to cosmic radiation at or near the Earth’s surface – a direct measure of transport, storage, and erosion processes.
The results show that some of the zircons remained on Earth’s surface for more than a million years before they were finally deposited. Particularly striking is a phase of change from long-stored, heavily ‘weathered’ sediments from the time of high global temperatures in the middle Eocene to more dynamic transport with shorter residence times thereafter. This change coincides with fluctuations in sea level and tectonic processes and reflects a fundamental change in the dynamics of the landscape. The study thus reveals how closely climate, tectonics, and sediment transport are linked over geological time periods.
“The method developed in Cologne for cosmogenic krypton in zircons allows us for the first time to quantitatively record the surface history of zircon-containing sediments in very old geological systems,” says Professor Dr Tibor J. Dunai from the University of Cologne’s Institute of Geology and Mineralogy. “Until now, such studies were limited in by the relatively short half-lives, on geological timescales, of other commonly used cosmogenic nuclides.”
In the long term, the method opens new perspectives for studying old, tectonically stable continents whose landscape histories were previously difficult to quantify. The researchers expect that cosmogenic krypton can also be used in other regions in the future to better understand the influence of climate and environmental changes on the Earth’s surface over millions of years.
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: Universities of Cologne
Reference Number: es011326_01
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