The physics behind the method is elegant. Beryllium-10 is a radioactive isotope forged when galactic cosmic rays smash into oxygen and nitrogen atoms high in the atmosphere, a process called spallation. Because Earth’s magnetic field deflects charged cosmic-ray particles, the production rate of beryllium-10 rises whenever the field weakens. Between 60 and 66 percent of the isotope is produced in the stratosphere, and models indicate that roughly half of the beryllium-10 eventually deposited over Antarctica actually originates at lower latitudes. When the geomagnetic dipole moment drops, production climbs, and the isotope rains down onto the polar ice sheet, where it is locked into annual layers of snow that compress into ice over millennia.

The star of the new record is the Iceland Basin Excursion, an event around 190,000 years ago that is widely regarded as the strongest geomagnetic excursion of the Brunhes chron, the period of normal polarity covering roughly the last 780,000 years. In the Talos Dome ice, the beryllium-10 flux rises to between 1.59 and 2.08 times its background level during a plateau lasting from about 192,000 to 185,600 years ago, with an uncertainty of roughly 1,400 years on each bound. That seven-thousand-year interval of extremely low field strength is consistent with sedimentary estimates suggesting the dipole collapsed by 70 to 80 percent, and it places the Iceland Basin Excursion in the same league as the famous Laschamps event of 41,000 years ago.

Perhaps the most striking feature of the event is its asymmetry. The Talos Dome data show a rapid decline of the dipole followed by a slow, three-step recovery, a pattern already seen in the Dome Fuji ice core and in western equatorial Pacific sediments. Intriguingly, this shape is the temporal opposite of what is observed during full polarity reversals, which typically involve a slow decay of the field followed by an abrupt recovery once the new polarity establishes itself. The authors argue that this consistent asymmetry across both the Iceland Basin and Laschamps excursions may reveal a fundamental difference between the dynamics of excursions and reversals, and they urge that it be carefully considered in future geodynamo modeling efforts.

Beyond the headline event, the record resolves two weaker disturbances that had long been mired in confusing nomenclature. A prolonged dipole decrease between about 218,500 and 206,000 years ago is associated with the Pringle Falls Excursion, while a briefer minimum centred at 242,000 years ago corresponds to the Mamaku Excursion, first recorded in volcanic rocks from New Zealand’s Taupo volcanic zone. Both show beryllium-10 flux enhancements of 1.24 to 1.63 times background. This is the first time either of these moderate-amplitude events has been discussed in an ice core, and their appearance only in flux, rather than in raw concentration, underscores a technical lesson: because snow accumulation rates varied substantially across the warm substages of Marine Isotope Stage 7, concentrations alone can mask genuine production signals.

The team also confronted a subtle artifact that could have corrupted the paleomagnetic interpretation. They identified 40 short-lived minima in beryllium-10 concentration, each confined to one or two consecutive 20-centimeter samples. These minima consistently coincide with spikes in major ion concentrations, including sodium, chloride, and calcium, which originate from such diverse sources as sea spray, crustal dust, and volcanic emissions. The statistical association is highly significant, and calcium-rich conditions in particular stand out: 32 percent of the beryllium-10 minima exceed 15 parts per billion of calcium, compared with only 13 percent of background samples. Because the ions come from unrelated sources, the team rules out atmospheric explanations and instead points to post-depositional processes deep in the ice.

Their favored hypothesis involves the migration of impurities along ice crystal boundaries. In the deepest, warmest sections of ice cores, large ice grains and enhanced impurity relocation can bind beryllium into dust-rich aggregates at grain boundaries, which the ion-exchange chemistry used to extract the isotope does not fully recover, producing apparent concentration minima. Crucially, once these artifacts are identified and removed, the long-term flux signal remains intact, and the geomagnetic record survives. The finding carries a practical warning for projects hunting ice older than 1.5 million years, such as Beyond EPICA: highly altered deep ice may require improved extraction protocols that account for in-ice remobilization of cosmogenic nuclides.

Cross-checking against other archives proved remarkably successful. The Talos Dome flux variations agree closely with the Dome Fuji beryllium-10 record over their overlapping interval, and both mirror the authigenic beryllium-10 to beryllium-9 ratios measured in marine sediment cores. Fine-scale features, including a short-lived recovery at 182,000 years ago and a flux minimum near 178,000 years ago, appear in both ice cores and ocean sediments, offering valuable tie points for synchronizing paleoclimate archives across entirely different media. One apparent discrepancy, a roughly 3,000-year offset between the oceanic and ice records, the authors attribute to uncertainties in the marine age model rather than a genuine physical lag, noting that the offset does not vary between glacial and interglacial intervals as an ocean-circulation effect would.

The study also documents a persistent puzzle of Antarctic beryllium geochemistry: absolute fluxes at Dome Fuji run nearly twice as high as those at Talos Dome, a pattern that persists into the recent past and appears unrelated to glacial-interglacial climate variability. The team suggests regional differences in atmospheric deposition, including a transition from wet to dry deposition south of 75 degrees south latitude and enhanced stratosphere-troposphere exchange over the highest domes. Importantly, this affects amplitude but not timing, so relative variations across sites still faithfully track changes in cosmic-ray production.

The implications reach beyond paleomagnetism. A reliable, well-dated record of dipole collapses provides a global synchronization tool for aligning ice, sediment, and volcanic archives across the Pleistocene, refining age models where independent dating is scarce. The Iceland Basin Excursion, with its prolonged seven-millennium low field and interglacial setting, also offers an analogue for reassessing claims that the Laschamps event disrupted atmospheric chemistry and ecosystems. And at a deeper level, each high-resolution record of the geodynamo’s erratic behavior brings scientists closer to answering a fundamental question: whether the seemingly random fluctuations of Earth’s magnetic field are truly stochastic, or the signature of deterministic but chaotic dynamics churning in the liquid iron core, two thousand miles beneath our feet.

Subject of Research: Reconstruction of geomagnetic dipole intensity variations from 170 to 270 ka BP using atmospheric beryllium-10 in the Talos Dome East Antarctic ice core

Article Title: Atmospheric 10Be from Talos Dome (East Antarctic) ice core records geomagnetic dipole intensity from 170 to 270 ka BP

Article References: Lamothe, A., Bard, E., Thouveny, N., Auriol, E., Severi, M., Traversi, R., De Angelis, M., Wilhelms, F., Mulvaney, R., Zaidi, F., Aumaitre, G., Keddadouche, K., & Baroni, M. (2026). Atmospheric 10 Be from Talos Dome (East Antarctic) ice core records geomagnetic dipole intensity from 170 to 270 ka BP. Geochronology, 8(2), 351-371. https://doi.org/10.5194/gchron-8-351-2026

Image Credits: AI Generated

DOI: 10.5194/gchron-8-351-2026

Keywords: beryllium-10, geomagnetic excursion, Iceland Basin Excursion, Pringle Falls Excursion, Mamaku Excursion, Talos Dome ice core, East Antarctica, cosmogenic radionuclides, geodynamo, paleomagnetism, ice core chronology, Marine Isotope Stage 7

At first glance, marine sediments found high in a mountain landscape may appear to be a simple indication that the land rose. In reality, determining how and when that happened requires separating several processes that can alter the elevation of ancient shorelines. Global sea level has repeatedly risen and fallen in response to the growth and melting of continental ice sheets. Local tectonic deformation can tilt or displace sedimentary basins, while erosion can remove parts of the original coastal environment. The research team therefore combined multiple independent techniques to establish the age, environmental setting, and original water depth of the TOL-1 deposits. Together, these methods transform the outcrop from an isolated geological curiosity into a precise record of regional uplift and the deep Earth forces that produced it.

The researchers used calcareous nannofossils and foraminifera—microscopic marine organisms whose shells and evolutionary changes are widely used to date sedimentary rocks—to constrain the age of the deposits. Calcareous nannofossils are planktonic algae that leave behind tiny calcium carbonate plates, while foraminifera are single-celled organisms that build distinctive mineral shells. Because different species occupied particular intervals of geological time and responded to changing marine conditions, their fossil assemblages can provide both biostratigraphic age markers and environmental information. The team also analyzed paleomagnetism, the record of ancient geomagnetic field behavior preserved by magnetic minerals in sediments. These measurements added an independent chronological framework, reducing the risk that the age estimate would depend on a single type of evidence.

Stable isotope measurements supplied another layer of information. Ratios of oxygen and carbon isotopes preserved in carbonate fossils and sediments can reflect changes in seawater chemistry, temperature, ice volume, and biological productivity. They do not function as a geological clock on their own, but when combined with fossil evidence and magnetic signatures, they can help identify the broader climatic setting in which marine deposition occurred. The TOL-1 section contains a combination of signals consistent with deposition during MIS 7, an interval marked by substantial climate variability and repeated changes in global ice volume. Establishing that the sediments formed during this specific period is crucial because it allows the ancient shoreline to be compared with known sea-level conditions rather than treating its modern elevation as a direct measure of tectonic motion.

One of the most innovative elements of the study was the reconstruction of the basin’s ancient water depth using ostracods. Ostracods are tiny crustaceans enclosed in hinged shells, and their communities are highly sensitive to salinity, water depth, oxygenation, temperature, and the connection between a basin and the open sea. Because different ostracod species prefer different habitats, fossil assemblages can act as biological depth indicators. By identifying the species preserved in the TOL-1 sediments and comparing them with modern ecological distributions, the researchers estimated the paleobathymetry—the water depth at which the deposits accumulated. This correction is essential: a layer now located at 1,177 meters elevation may originally have formed below sea level, but the amount of submergence must be estimated before the total tectonic uplift can be calculated.

The resulting uplift rate is striking even by the standards of active mountain belts. An average rise of approximately 5.2 meters per thousand years means that, over 100,000 years, the surface could be displaced upward by roughly 520 meters, assuming the rate remained broadly representative over that interval. Geological uplift is rarely perfectly constant, and the reported value is an average derived from the age and elevation of the deposits after accounting for their former marine setting and global sea-level changes. Even with that qualification, the rate indicates exceptionally rapid vertical motion. The study places a rare numerical constraint on when the Mut Basin changed from a marine environment into part of the elevated Central Anatolian Plateau, linking a visible landscape feature to processes occurring tens of kilometers beneath the surface.

The broader significance lies in the tectonic setting of southern Türkiye, where the Anatolian region sits at the intersection of major convergent plate systems. Africa and Arabia move northward relative to Eurasia, while the Anatolian block is squeezed westward between surrounding faults and plate boundaries. In such environments, uplift can be produced by crustal shortening, fault-related deformation, changes in the thickness of the crust, or buoyant flow in the underlying mantle. The authors discuss deep-seated mechanisms including slab break-off and mantle flow as possible drivers of the rapid elevation gain. Slab break-off occurs when a dense piece of oceanic lithosphere that has descended into the mantle detaches from the portion still attached to a subducting plate. The removal of that dense downward pull can allow hot mantle to rise, increasing buoyancy beneath the overriding crust and promoting rapid surface uplift.

Mantle flow may amplify that effect. As a detached slab sinks or reorganizes at depth, the surrounding mantle can move into the space it leaves behind. Hot, relatively buoyant material rising beneath a region can support the crust from below, while changes in stress and temperature may trigger additional deformation in the upper plate. The TOL-1 record does not simply image these processes directly; instead, it provides a time-stamped surface response that geodynamic models must explain. That distinction is important. Rocks at the surface preserve the consequences of deep Earth dynamics, while seismic imaging, plate-kinematic reconstructions, and numerical models are needed to test the precise mechanism. By connecting the age of marine deposits with their present elevation, the study supplies the kind of quantitative benchmark that can distinguish gradual plateau growth from episodes of unusually rapid uplift.

The discovery also changes how scientists may interpret ancient marine deposits elsewhere in the Mediterranean and surrounding mountain belts. Elevated shorelines and marine sediments are often used to reconstruct former sea levels, but tectonic movement can complicate those reconstructions. If an ancient coastal deposit has risen hundreds or thousands of meters, its current position records both global climate-driven sea-level change and local vertical motion. The TOL-1 section is particularly valuable because it preserves several complementary indicators in one location: fossil communities, magnetic signatures, isotope data, and sedimentary evidence of a former marine environment. Such integrated sections are uncommon, and they can serve as calibration points for regional models of plateau development, basin closure, erosion, and earthquake-related deformation.

For Selma Sarı, the publication represents the culmination of early-career research conducted at Università degli Studi Roma Tre, but its implications extend far beyond an individual field site. The study presents southern Türkiye as a natural laboratory where a marine basin, a rising plateau, and active plate convergence can be read in the same sequence of rocks. Its central message is both dramatic and precise: landscapes that appear stable over a human lifetime may undergo astonishing vertical change when viewed across geological time, and those changes can sometimes be measured with meter-scale averages per millennium. By identifying the highest known late Middle Pleistocene marine deposits and reconstructing the forces that lifted them, the researchers have turned an ancient seabed into a vivid record of Earth’s restless interior—and a compelling example of how microscopic fossils can reveal the movements of entire mountain plateaus.

Subject of Research: Cells

Article Title: The world’s highest late Middle-Pleistocene marine deposits on the southern margin of the Central Anatolian Plateau (southern Türkiye)

News Publication Date: 25-Aug-2026

Web References: https://doi.org/10.1130/G55209.1

References: Sarı, S., et al. (2026), Geology, “The world’s highest late Middle-Pleistocene marine deposits on the southern margin of the Central Anatolian Plateau (southern Türkiye),” DOI: 10.1130/G55209.1

Image Credits: Photo credit: Selma Sarı.

Keywords: Central Anatolian Plateau, Türkiye, Mut Basin, TOL-1 section, Middle Pleistocene, Marine Isotope Stage 7, marine deposits, tectonic uplift, slab break-off, mantle flow, paleomagnetism, foraminifera, calcareous nannofossils, ostracods, paleobathymetry, marine geology, Earth sciences