Articles | Volume 45, issue 1
https://doi.org/10.5194/jm-45-177-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/jm-45-177-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Unraveling Southern Ocean diatom diversity across the Eocene–Oligocene transition
Volkan Özen
CORRESPONDING AUTHOR
Freie Universität Berlin, Institute for Geological Sciences, Malteserstraße 74–100, 12249 Berlin, Germany
Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, 10115 Berlin, Germany
Johan Renaudie
Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, 10115 Berlin, Germany
David Lazarus
Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, 10115 Berlin, Germany
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We studied how diatoms (photosynthetic algae with silica shells) responded to major climatic and ocean changes between 38 and 32 million years ago, when the climate shifted into a colder state and Antarctic ice sheets expanded. Equatorial Atlantic sediment records show a sharp reorganization of diatom communities and an extinction pulse around 33.5 million years ago, coinciding with the largest cooling step of this transition.
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We studied diatom fossils from the Southern Ocean to understand how ocean productivity changed ~40–30 million years ago during a major climate shift marked by the onset of permanent Antarctic glaciation and global cooling. We found striking shifts in diatom productivity, revealing critical changes in ocean circulation and nutrient supply. Our results show how these microscopic organisms may have influenced climate, acting as a geological force that shaped global climate over time.
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We studied how diatoms (photosynthetic algae with silica shells) responded to major climatic and ocean changes between 38 and 32 million years ago, when the climate shifted into a colder state and Antarctic ice sheets expanded. Equatorial Atlantic sediment records show a sharp reorganization of diatom communities and an extinction pulse around 33.5 million years ago, coinciding with the largest cooling step of this transition.
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Clim. Past, 21, 1431–1441, https://doi.org/10.5194/cp-21-1431-2025, https://doi.org/10.5194/cp-21-1431-2025, 2025
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We provide a new compilation of rates at which sediments deposited in the deep sea over the last 70 million years. We highlight a bias, linked to the drilling process, that makes it more likely for high rates to be recovered for younger sediments than for older ones. Correcting for this bias, the record shows, contrary to prior estimates, a more stable history, thus providing some insights on the past mismatch between physico-chemical model estimates and observations.
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A global-scale compilation of Palaeogene diatomite occurrences shows how palaeogeographic and palaeoceanographic changes impacted diatom accumulation, especially in the middle Eocene. Diatomite deposition dropped in epicontinental seas between ~ 46 and ~ 44 Ma, while diatom accumulation began around 43.5 Ma in open-ocean settings. The compilation also shows an indirect correlation between Palaeogene climate fluctuations and diatomite deposition in shallow-marine and freshwater environments.
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This study evaluates the use of automatic classification using AI on eight closely related radiolarian species of the genus Podocyrtis based on MobileNet CNN. Species belonging to Podocyrtis are useful for middle Eocene biostratigraphy. Numerous images of Podocyrtis species from the tropical Atlantic Ocean were used to train and validate the CNN. An overall accuracy of about 91 % was obtained. Additional Podocyrtis specimens from other ocean realms were used to test the predictive model.
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Short summary
The Eocene–Oligocene transition was a pivotal interval in Earth's geological history, marked by cooling and Antarctic glaciation. Our research explores how Southern Ocean diatoms responded to these changes. By analyzing records from multiple sites, we revealed previously unrecognized diatom diversity, and identified distinct patterns in diversity and extinction. These findings deepen our understanding of the interplay between climatic perturbations and the biosphere.
The Eocene–Oligocene transition was a pivotal interval in Earth's geological history, marked by...