idw – Informationsdienst Wissenschaft
Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
When a few millimetres can mean a difference of four million years: as part of the BROMACKER project, a team of researchers, including Dr Lorenzo Marchetti from the Museum für Naturkunde Berlin, discovered that the famous fossil deposit between Tambach-Dietharz and Georgenthal in the Thuringian Forest is older than previously thought.
Analysis of a volcanic ash tuff layer, only a few millimetres thick and discovered during excavations in 2024, revealed that the fossil-bearing Bromacker rocks are 294 million years old — four million years older than previously thought. These findings have now been published in the journal Gondwana Research.
“When we uncovered the dark, reddish-purple ash layer, the difference to the surrounding rock was immediately apparent. We were hopeful that we had finally found material that could be dated,” says Sophie König, a museologist working at the Friedenstein Stiftung Gotha in the framework of the BROMACKER project, who is also a co-author of the recently published paper. “I was surprised that the rock sample actually contained usable zircons. We are delighted to have added another important scientific puzzle piece to the highly successful BROMACKER project.”
To date an ash layer, scientists use the internal clocks of certain minerals incorporated into rocks. In this case, they considered the mineral zircon, which, despite being very small, has an excellent long-term memory. Zircon crystals were extracted from a rock sample collected at Bromacker by researchers at Friedrich-Schiller-Universität in Jena and analysed radiometrically at TU Bergakademie Freiberg.
This is the only facility in Germany where the history of rocks can be traced using the U-Pb CA-ID-TIMS method, which is a type of uranium-lead dating, in a metal-free clean room laboratory that enables their age to be determined with high precision.
The results of the new dating method have implications for the study of ecosystems and fossils from other deposits of a similar age, such as those at Bromacker, which formed on the supercontinent Pangaea. Thanks to the correlation with the Bromacker fossils, which have now been accurately dated, the age of these fossils can now be better determined.
“This extraordinary fossil deposit provides a wealth of information about Permian ecosystems and required precise dating to establish it as a global reference point for biostratigraphic, palaeoclimatic and evolutionary biology studies. The careful exploration of the Bromacker site made this unexpected yet crucial discovery possible: a layer of ash containing well-preserved zircon crystals,” says Dr Lorenzo Marchetti, the paper's lead author and a scientist at the Museum für Naturkunde Berlin.
The new age has impacted the scientific understanding of early ecosystems and land vertebrates. The food pyramid as we know it today developed earlier than previously thought. The time span between the first appearance of herbivores and the development of modern food webs was shorter than initially thought, proving that Bromacker organisms evolved more rapidly. Thanks to new dating methods, it is now clear that these evolutionary innovations and the transition to a more seasonal climate occurred much earlier than the scientific community had previously assumed.
"The redating of the fossil deposit is part of the BROMACKER project, which is funded by the German federal government and the Free State of Thuringia. It is a prime example of what can be achieved scientifically when experts from a variety of institutions collaborate on a joint project. "Bromacker has evolved into an innovative, interdisciplinary research and science communication programme that draws on decades of international collaboration. It has enormous potential for the future," says Dr Tom Hübner, head of the Bromacker project at the Friedenstein Stiftung Gotha.
Marchetti, L., Stubenrauch, J., Käßner, A., Tichomirowa, M., König, S., Pint, A. & Voigt, T. (2026). First high-precision radioisotopic age from the Permian Bromacker lagerstätte (Tambach Formation, Germany) and implications for biochronology and biota evolution. Gondwana Research, https://doi.org/10.1016/j.gr.2026.02.005.
Criteria of this press release:
Journalists
Biology, Environment / ecology, Geosciences
transregional, national
Research results, Scientific Publications
English
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