A team of researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in collaboration with the Dresden University of Technology (TUD Dresden) and the Australian National University (ANU), has discovered an unusual accumulation of the radioactive isotope beryllium-10 (¹⁰Be) in samples taken from the Pacific seafloor. This unexpected phenomenon, which could be due to changes in ocean currents or astrophysical events that occurred approximately 10 million years ago, may become a key temporal marker for geology. The research findings have been published in the journal Nature Communications.

Radionuclides such as beryllium-10 are radioactive isotopes that allow scientists to date archaeological and geological samples. A well-known example is radiocarbon dating (carbon-14), which is used to determine the age of organic remains up to 50,000 years old.

However, for older samples, scientists rely on isotopes with a longer half-life, such as ¹⁰Be, which has a half-life of 1.4 million years. This isotope is generated in the atmosphere when cosmic rays interact with oxygen and nitrogen and then deposits on Earth through precipitation, accumulating on the ocean floor.

Pacific Berilium anomaly
a Photo of the ferromanganese crust VA13/2-237KD. A 1 euro coin and a 50 Australian cents coin are used as size references. b Locations of the ferromanganese crusts VA13/2-237KD (red star)20,21,32, SO142-4DR (blue star)35 and Crust-333 (yellow shaded area, exact location unknown due to resource protection). The major bottom (blue line) and surface (red line) ocean currents of the thermohaline circulation are indicated. Credit: D. Koll et al. / Esri, GEBCO, Garmin, NaturalVue

The HZDR research team analyzed geological samples obtained from ferromanganese crusts on the Pacific seafloor. These crusts, composed mainly of iron and manganese, form over millions of years through an extremely slow sedimentation process. To determine their age, scientists used Accelerator Mass Spectrometry (AMS), a technique that allows precise identification of ¹⁰Be traces.

To the team’s surprise, the results indicated a concentration of ¹⁰Be nearly twice as high as expected in a layer corresponding to 10 million years ago. To rule out contamination, additional samples from the same region were analyzed, confirming the anomaly. This finding represents strong evidence of a global event that altered the distribution of ¹⁰Be on Earth.

The researchers have proposed two possible explanations for this phenomenon. One theory suggests that a change in ocean currents occurring between 10 and 12 million years ago may have temporarily altered the distribution of ¹⁰Be, concentrating it in certain regions of the Pacific. This would be linked to significant changes in ocean circulation, particularly in the Antarctic region.

Pacific Berilium anomaly
Schematic depiction of production and incorporation of cosmogenic 10Be into ferromanganese crusts. A pronounced anomaly in 10Be concentration about 10 million years ago was discovered. This anomaly has great potential as time marker for the Late Miocene. Credit: HZDR / blrck.de

The second hypothesis points to an astrophysical origin. It has been proposed that a nearby supernova may have increased the intensity of cosmic rays reaching Earth, leading to a rise in ¹⁰Be production in the atmosphere. Another possibility is that the planet passed through a dense interstellar cloud, which weakened the heliosphere’s protection, allowing greater exposure to cosmic rays.

The discovery of this anomaly could revolutionize the way geologists synchronize marine and terrestrial records over time. Currently, no universal temporal markers exist for periods spanning millions of years. If this ¹⁰Be accumulation is found in other parts of the world, it could serve as a global reference for geological dating, enabling more precise synchronization of past events.

To determine the exact origin of the anomaly, the HZDR team plans to expand its research and analyze samples from other parts of the world. Additionally, they hope other research groups will join the search for answers. If the phenomenon is detected in widely dispersed regions, the astrophysical event hypothesis would be reinforced. Conversely, if it is only found in specific areas, the most likely explanation would be changes in ocean currents.

SOURCES

Helmholtz Zentrum Dresden Rossendorf

Koll, D., Lachner, J., Beutner, S. et al. A cosmogenic 10Be anomaly during the late Miocene as independent time marker for marine archives. Nat Commun 16, 866 (2025). doi.org/10.1038/s41467-024-55662-4

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