The Qaidam Basin is a natural laboratory for studying aridity. Wedged between the Kunlun, Altyn Tagh, Qilian, and Ela mountains on the northeastern Tibetan Plateau, the basin is one of the most enclosed landscapes in Asia. Modern annual precipitation there ranges from a meager 50 to 200 millimeters, while evaporation soars to around 3,000 millimeters, producing a hyper-arid environment where salts such as halite, gypsum, and carbonates accumulate in thick layers. Because the basin sits far from major moisture sources and lies in the rain shadow of the Tibetan Plateau, any signal of increased rainfall is immediately meaningful, and any record of past wetting or drying speaks directly to the reach of the East Asian summer monsoon.

The new study, led by Zeng Luo of Hunan University of Arts and Science with colleagues from Lanzhou University, Hubei Normal University, Linyi University, and other institutions, focuses on the Gansen section, a sedimentary sequence exposed on the northwestern margin of the basin. Previous work had already established a paleomagnetic timeline for the section, anchoring 453 meters of strata to the geomagnetic polarity time scale with ten age control points spanning roughly 3.6 to 1.8 million years ago. Building on that framework, the team collected 149 samples and measured two independent climate-sensitive properties: environmental magnetic parameters and median grain size.

The magnetic approach hinges on a clever ratio. Frequency-dependent magnetic susceptibility, which responds to tiny pedogenic grains of magnetite formed during wet weathering, is divided by hard isothermal remanent magnetization, which reflects hematite produced under drier conditions. The resulting ratio, known as χfd/HIRM, tracks the balance between wet and dry weathering regimes and has proven sensitive to precipitation in arid and semiarid settings. Median grain size provides a complementary signal, because coarser particles in closed, shallow lake environments generally indicate stronger runoff and hydrodynamic energy, both of which scale with rainfall. Together, the two proxies form a paired record of hydroclimatic change.

When the team combined the new measurements with previously published data for the interval from 3.25 to 2.95 million years ago, they obtained an integrated precipitation record covering nearly the entire Late Pliocene. The record divides naturally into three phases. From about 3.6 to 3.25 million years ago, χfd/HIRM values fluctuated widely between 9.2 and 105 times ten to the minus six amperes per meter, averaging 38.3, while median grain size averaged 10.48 micrometers. Three thick halite layers in the stratigraphy corresponded to low points in both proxies, marking pulses of intensified aridity. From 3.25 to 2.95 million years ago, the warm middle Piacenzian interval, both proxies rose and the halite layers vanished, signaling a wetter climate. After 2.95 million years ago, values declined, grain size coarsened and then dropped, and halite layers became more frequent, pointing to renewed drying.

The most striking result emerged from spectral analysis of the densely sampled interval between about 3.6 and 3.3 million years ago. Using the REDFIT procedure, which tests spectral peaks against a red-noise background, the researchers found that the strongest periodicity in the χfd/HIRM record sat near 100,000 years, while the grain-size record peaked closer to 125,000 years. Both signals fall squarely in the eccentricity band, the slow modulation of Earth’s orbital shape that has a far weaker direct effect on insolation than precession or obliquity. A sensitivity test with a coarser interpolation step confirmed that the eccentricity signal was not an artifact of data processing. This pattern contrasts sharply with the 20,000-year precession-dominated cycles that the same team had previously documented for the middle Piacenzian warm period.

Why would the same basin respond to different orbital rhythms at different times? The authors argue that the answer lies in the background climate state. During the wetter middle Piacenzian, when the East Asian summer monsoon was strong, summer moisture could penetrate deep into the Asian interior, and rainfall responded directly to the precessional forcing of summer insolation. During the earlier, drier interval around 3.6 to 3.3 million years ago, the monsoon’s reach was more limited, and precipitation appears to have been governed indirectly by large-scale boundary conditions. One plausible mechanism is that eccentricity-paced changes in high-latitude ice volume, potentially including fluctuations of the Antarctic ice sheet, modulated the thermal contrast between Eurasia and the surrounding oceans and altered ocean circulation patterns, which in turn influenced monsoon intensity. Supporting this idea, five high-value intervals in the precipitation proxies broadly match peaks in the benthic oxygen isotope stack, a global record of ice volume, and the two records show similar filtered variations to the isotope stack in the 40,000-year obliquity band as well.

The broader context strengthens the case. Because large Arctic ice sheets did not develop until roughly 2.7 million years ago, Antarctic variability was likely the dominant high-latitude ice signal during the Late Pliocene, making it a plausible mediator of the eccentricity-scale precipitation signal. Similar nonlinear responses to insolation forcing have been documented elsewhere in North China, including 100,000-year eccentricity cycles in magnetic susceptibility records from the Xinding Basin and in rubidium-strontium ratios from the Sanmenxia Basin. Pollen records from the SG-1b core in the western Qaidam Basin likewise revealed a strong link between 100,000-year precipitation cycles and eccentricity forcing during the interval from 3.5 to 3.0 million years ago. The new Gansen record thus fits into a growing picture in which the monsoon’s orbital fingerprint depends on the prevailing climate regime.

The implications reach beyond the Pliocene. The middle Piacenzian warm period, with atmospheric carbon dioxide concentrations of 400 to 450 parts per million, elevated global temperatures, higher sea levels, and small Arctic ice sheets, is widely regarded as one of the best geological analogs for future anthropogenic warming. Climate model simulations suggest that enhanced land-sea thermal contrast during that interval intensified and westward-extended the western Pacific subtropical high, strengthening the East Asian summer monsoon and pushing its precipitation boundary northwestward. If the same mechanism operates under continued modern warming, the Qaidam Basin and other parts of the arid Asian interior could receive increased summer moisture in the decades ahead, a possibility with significant consequences for water resources in a region where every millimeter of rain matters.

At the same time, the study carries a caution. After about 2.95 million years ago, the record shows clear signs of intensifying aridification, with more frequent salt layers and declining proxy values, consistent with other evidence that the western Qaidam Basin became drier no later than around 3 million years ago. The precession-dominated wet pattern of the middle Piacenzian was therefore not a permanent feature of the Late Pliocene but a window tied to specific background conditions. By showing that the dominant periodicity of precipitation can shift from eccentricity to precession scales as climate states change, the research underscores a fundamental point for paleoclimate science and for projections of future hydrology alike: the response of regional rainfall to orbital forcing is not fixed, and understanding when and why it changes may be as important as knowing the forcing itself.

Subject of Research: Orbital-scale precipitation variability in the western Qaidam Basin during the Late Pliocene

Article Title: Orbital-scale precipitation variations in the western Qaidam Basin during the Late Pliocene: evidence from magnetic parameters and median grain-size

Article References: Luo, Z., Wang, H., Yu, X., Zhang, Z., Song, Z., Yang, J., Chen, W., Su, Q., Lu, Y., & Hua, S. (2026). Orbital-scale precipitation variations in the western Qaidam Basin during the Late Pliocene: evidence from magnetic parameters and median grain-size. Climate of the Past, 22(10), 1913-1925. https://doi.org/10.5194/cp-22-1913-2026

Image Credits: AI Generated

DOI: 10.5194/cp-22-1913-2026

Keywords: Qaidam Basin, Late Pliocene, East Asian summer monsoon, orbital forcing, eccentricity, precession, paleoclimate, magnetic susceptibility, grain size, Tibetan Plateau, aridification, mid-Piacenzian warm period

The Jradzor section, dated by multiproxy methods to between 4.3 and 3.03 million years ago, contains 19 fossiliferous horizons and at least 48 identified vertebrate taxa. Almost all of the hipparionine material comes from a single horizon, JZ-7, corresponding to lahar deposits of early MN16 age, with just two additional isolated specimens from pyroclastic flow deposits. The dramatic volcanic setting helps explain the remarkable preservation: teeth, mandibles, vertebrae, humeri, radii, metapodials, ankle bones and phalanges were rapidly buried and sealed, giving researchers an unusually complete picture of a horse population that lived at the twilight of the hipparionine lineage.

Hipparionine horses are among the most successful and confusing groups in the mammalian fossil record. Defined by an isolated, ovoid protocone on their upper cheek teeth and three-toed feet, they first entered the Old World from North America around 11.2 million years ago in an immigration event long known as the Hippotherium Datum. They diversified explosively across Eurasia, reaching their peak of taxonomic and ecological diversity during the Turolian age of the Late Miocene. But at the end of the Miocene, a sharp extinction event wiped out several hipparionine genera in South and West Eurasia, leaving only a handful of lineages, including Cremohipparion, Proboscidipparion, Plesiohipparion, Eurygnathohippus and Baryhipparion, to carry on into the Pliocene.

The species at the heart of the new study, originally named Hipparion longipes in 1952 from Pavlodar in Kazakhstan, has been shuffled between genera for decades. Recent work placed it in Plesiohipparion almost exclusively on the basis of the extreme gracility and elongation of its metapodials, the long central cannon bones of its limbs. The Jradzor fossils, however, preserve both teeth and limb bones in combination, allowing the researchers to test that assignment against the full suite of diagnostic characters rather than measurements alone.

The anatomical evidence proved decisive. The Jradzor horses show a constellation of features matching the genus Cremohipparion: an incisor row with a non-atrophied third incisor, an isolated protocone on the deciduous upper cheek tooth, lower cheek teeth with rounded metaconid and metastylid, shallow V- to U-shaped linguaflexids, a hypoflexid that separates the metaconid and metastylid on lower molars but not on premolars, and the general absence of the pli caballinid and ectostylid. Crucially, they lack the derived double knot and persistent pli caballinid that define Plesiohipparion. On this combined evidence, the authors formally reassign both Hipparion longipes and the related Hipparion fissurae to Cremohipparion, creating the new combinations Cremohipparion longipes and Cremohipparion fissurae.

The methodology behind these conclusions is as instructive as the result. The team measured every specimen to a precision of 0.1 millimeters and then, before running any statistics, tested which measurements were actually independent of one another using Spearman rank correlations and Mantel tests. This preliminary analysis revealed a serious pitfall in earlier work: many commonly used variables, such as metapodial length and distal articular width, are strongly autocorrelated. Principal component analysis performed on autocorrelated variables can overestimate the variance captured by the first component, artificially compressing the apparent differences between taxa. The study shows that when this bias is controlled for, the discriminating power of the analyses improves and the boundaries between Cremohipparion, Plesiohipparion and Proboscidipparion become far clearer.

Paleobiological estimates add vivid detail to the animal itself. Using established equations based on metapodial dimensions, the researchers calculated body weights, shoulder heights and gracility indices for the Jradzor horses. All specimens fall into the very slender category, with gracility indices below 13.5, averaging 11.2 on the metacarpal and a remarkable 9.5 on the metatarsal. Combined with true hypsodont cheek teeth, whose hypsodonty index exceeds 5, the picture is of a large, long-legged, highly cursorial grazer adapted to open and dry environments, exactly the kind of animal expected as cooling climates and expanding C4 grasslands transformed Eurasian landscapes during the Pliocene.

The reclassification ripples outward across geography as well. The revised distribution of Cremohipparion longipes traces a species that likely originated in Central Asia, as indicated by its record at Pavlodar in Kazakhstan, spread to the Middle East at Baynunah in the United Arab Emirates, and reappears in the late Pliocene at Megalo Emvolon in Greece, at Calta in Turkey and now at Jradzor in Armenia. Meanwhile, Hipparion cf. longipes from Akkasdagi in Turkey is tentatively reidentified as Cremohipparion cf. fissurae, extending the known range of that species far beyond its type locality at Layna in Spain. The large, slender-limbed Cremohipparion from Ruscinian sites on the Iberian Peninsula, including La Gloria 4, La Calera, Orrios-1 and Villalba Alta Rio 1, is confirmed as morphologically distinct from Cremohipparion fissurae and probably endemic to Spain during MN14.

Perhaps most strikingly, the dispersals of Cremohipparion longipes appear to track dramatic environmental upheavals in the Paratethys region. Its appearance in Central Asia coincides with the Khersonian Drying, when the Eastern Paratethys Sea shrank and exposed vast new territories of Central Eurasia. Its later presence at Jradzor and other MN15 to early MN16 sites correlates with the period when the Caspian Sea contracted to its smallest extent, the Productive Series interval, an event attributed to climate change, tectonic reorganization, or both. The following Akchagylian stage brought a humid climate and a different hipparionine, Plesiohipparion rocinantis, at the nearby site of Kvabebi in Georgia, underscoring how sensitive these horses were to shifting environments.

Beyond the taxonomy, the study delivers a pointed methodological message: the evolutionary history of hipparionine horses cannot be resolved by measurements alone. Uncontrolled statistical analyses of autocorrelated data can lead to erroneous generic assignments, as the long misplacement of Hipparion longipes in Plesiohipparion demonstrates. Instead, the authors argue for an integrative approach that combines morphological observation, morphometrics, paleoecology, biostratigraphy and biogeography. With three-toed horses persisting in China until the latest Pliocene and even briefly coexisting with the modern one-toed genus Equus at sites like Roca-Neyra in France, the group’s final chapter is still being written, and the fossils from an Armenian mine are helping to set the record straight.

Subject of Research: Taxonomic revision of Late Pliocene hipparionine horses from Jradzor, Armenia, and the reassignment of Hipparion longipes and Hipparion fissurae to the genus Cremohipparion

Article Title: The Hipparionini horses ( Equidae , Perissodactyla , Mammalia ) from the Late Pliocene of Jradzor (Armenia)

Article References: Becker, D., Mouhat Bourquard, M., Maridet, O., & Vasilyan, D. (2026). The Hipparionini horses (Equidae, Perissodactyla, Mammalia) from the Late Pliocene of Jradzor (Armenia). Swiss Journal of Palaeontology, 145, 625-653. https://doi.org/10.3897/sjp.145.189856

Image Credits: AI Generated

DOI: 10.3897/sjp.145.189856

Keywords: Hipparionini, Cremohipparion longipes, Jradzor, Armenia, Late Pliocene, paleontology, Equidae, taxonomy, morphometrics, Plesiohipparion, biogeography, hypsodonty

The central process at work is silicate weathering, a cornerstone of the long-term carbon cycle. When atmospheric carbon dioxide dissolves in rainwater and soil moisture, it forms carbonic acid, a weak acid capable of attacking the crystal lattices of silicate minerals such as feldspars and micas. As these minerals break down, the carbon carried in the acid is transformed into bicarbonate ions dissolved in water. Those ions can then travel through rivers to the ocean, where marine organisms incorporate the carbon into shells and other calcium carbonate structures that eventually settle into seafloor sediments. On geological timescales, this chain of reactions is one of the principal mechanisms by which Earth regulates atmospheric carbon dioxide and, with it, global temperature.

What makes the new analysis striking is its emphasis on drylands as an underappreciated locus for this chemistry. Arid regions receive little rain, so they are often assumed to play a minor role in weathering-driven carbon uptake compared with humid tropical belts where rainfall and vegetation accelerate mineral dissolution. Yet drylands possess distinctive advantages. Intense temperature swings between day and night physically fracture rock surfaces, expanding the reactive area available to chemical attack. Sparse vegetation means that minerals lie close to the surface, exposed to occasional but chemically aggressive runoff events. And, crucially, wind continuously supplies fresh, finely ground dust derived from distant mountain ranges, delivering new reactive material to soils that would otherwise exhaust their weathering potential.

The research team assembled this picture by reconstructing dust deposition and weathering fluxes across eolian archives reaching back to the late Pliocene, an epoch that ended approximately 2.6 million years ago. The late Pliocene is a pivotal interval in Earth’s history: global temperatures were gradually declining, ice sheets were expanding across the Northern Hemisphere, and the modern pattern of arid belts and monsoon circulation was taking shape. By examining the mineralogical and geochemical signatures preserved in dust deposits, the authors were able to track how much silicate material was delivered to dryland soils and how efficiently that material captured carbon dioxide over time.

The results point to persistence rather than volatility. Despite the dramatic climatic oscillations of the past three million years—including the repeated glacial-interglacial cycles of the Pleistocene—the carbon dioxide uptake associated with silicate weathering in eolian drylands appears to have remained remarkably stable. This stability matters because the long-term carbon cycle depends on sinks that behave predictably across changing climates. If a major weathering sink were to weaken abruptly during cold or dry intervals, the balance between volcanic carbon emissions and carbon removal would shift, amplifying climatic swings. The apparent resilience of dryland weathering suggests it has instead acted as a steadying hand, damping rather than reinforcing fluctuations in the global carbon budget.

The mechanistic explanation for this resilience lies in the interplay between supply and demand. In humid regions, weathering rates often saturate: once soils are deeply leached and vegetation covers the landscape, additional carbonic acid cannot significantly accelerate mineral dissolution. Drylands, by contrast, tend to be supply-limited rather than transport-limited. Because chemical reaction rates are slow in arid conditions, freshly deposited dust accumulates in soils awaiting reaction. Even a modest increase in moisture—a stronger monsoon season, a rare intense storm—can mobilize carbonic acid through this stored inventory of fine particles, unlocking weathering that was chemically banked during drier periods. Over thousands to millions of years, this buffering behavior smooths out climatic variability, allowing the carbon sink to persist even as individual decades and millennia fluctuate between dustier and wetter regimes.

The study also carries implications for how scientists model Earth’s climatic future. Most Earth system models represent silicate weathering through simplified parameterizations tuned primarily to temperature, runoff, and lithology, with little explicit treatment of dust supply to arid soils. If eolian drylands contribute a stable and geologically meaningful fraction of global carbon uptake, then changes in dust generation driven by land use, desertification, and shifting wind patterns could subtly alter the trajectory of natural carbon sequestration in the coming centuries. The authors’ reconstruction provides a benchmark against which such model assumptions can be tested, anchoring simulations of deep-time climate in empirical records of dust and weathering chemistry.

There is also a deeper conceptual payoff. For decades, the narrative of drylands in climate science has been dominated by their vulnerabilities: expanding deserts, degrading soils, and human populations exposed to heat and water stress. This research adds a counterpoint, portraying the same environments as engines of planetary regulation. Fine dust lofted from the Sahara, the Gobi, and the world’s other great dust sources does not simply smother ecosystems downwind; it seeds soils with reactive minerals, fertilizes distant oceans with iron, and, according to this study, sustains a chemical removal of carbon dioxide that has operated without interruption since before the Ice Ages began. In that sense, the planet’s dustiest places have been among its most dependable climate stabilizers.

The late Pliocene baseline gives the finding particular weight for understanding the modern atmosphere. Around three million years ago, carbon dioxide concentrations were comparable in broad magnitude to levels considered plausible for the coming decades, and global mean temperatures were warmer than preindustrial values. Reconstructing how weathering sinks behaved under those conditions offers a natural experiment on how the carbon cycle responds to a warmer world. The persistence of dryland silicate weathering through the Pliocene-Pleistocene transition suggests that this sink is robust to the kinds of temperature and hydrological shifts currently under way, though the authors caution that the pace of modern anthropogenic change vastly exceeds the gradual forcing of the late Cenozoic.

As with any reconstruction spanning millions of years, uncertainties remain in translating geochemical proxies into precise fluxes, and the global significance of dryland weathering relative to mountain belts and tropical basins will continue to be debated. But the study’s core message is difficult to ignore: the long-term carbon cycle is woven together by processes operating in places that rarely attract attention. Every dust storm that darkens a distant sky carries within it a shipment of silicate minerals destined to react, slowly and invisibly, with carbonic acid drawn from the air. That humble reaction, repeated across arid landscapes for millions of years, has helped keep Earth’s thermostat within the range that allows oceans, ice sheets, and life to persist. In an era when humanity is rapidly adding carbon dioxide to the atmosphere, understanding the full inventory of natural sinks—including the silent work of wind-blown dust in the world’s drylands—has never been more urgent.

Subject of Research: Long-term silicate weathering and carbon dioxide uptake in eolian drylands since the late Pliocene

Article Title: Persistent silicate weathering and carbon dioxide uptake in eolian drylands since the late Pliocene

Article References: Zhang, C., Wu, H., Hu, B., Qiao, Y., & Guo, Z. (2026). Persistent silicate weathering and carbon dioxide uptake in eolian drylands since the late Pliocene. Communications Earth & Environment. https://doi.org/10.1038/s43247-026-04058-x

Image Credits: AI Generated

DOI: 10.1038/s43247-026-04058-x

Keywords: silicate weathering, eolian drylands, carbon dioxide uptake, long-term carbon cycle, late Pliocene, dust deposition, climate regulation, geochemistry, carbon sequestration, Communications Earth & Environment, Persistent, silicate