The new study, published in the journal Climate of the Past, focuses on a nearly 200-meter-thick stack of sedimentary rocks exposed near the village of Büyükteflek in the Çankırı Basin, at the northern edge of the Kırşehir Massif in central Anatolia. This region sits within Balkanatolia, a semi-continuous strip of land that stretched from the Alps to the Lesser Caucasus during the Paleogene and that biogeographers now recognize as a critical stepping stone between Asia and western Europe. During the Eocene, Balkanatolia was a mosaic of islands isolated by the Paratethys Sea to the north and east, the Neotethys Ocean to the south, and narrower seaways to the northwest. That isolation bred endemism: for millions of years, the province hosted its own distinctive cast of mammals found nowhere else. Only as tectonic shortening and falling sea levels stitched the islands together, first in the east through Anatolia and later in the west, did land connections to the rest of Laurasia begin to re-emerge.

To pin down the age of the Büyükteflek section, the researchers combined magnetostratigraphy, the record of ancient reversals of Earth’s magnetic field preserved in the rocks, with uranium–lead dating of interbedded volcanic ash layers and marine microfossil biostratigraphy. They drilled and oriented 110 core samples from red clays, silts, and paleosol carbonates, demagnetized them step by step in alternating fields and at progressively higher temperatures, and isolated the characteristic remanent magnetization carried by magnetite and hematite grains. Six distinct magnetic polarity zones emerged from the section. Correlating these with the geomagnetic polarity time scale, anchored by ash beds dated at about 32.1 and 32.6 million years ago, showed that the lower part of the section spans the Priabonian stage of the late Eocene, beginning around 37.7 million years ago, while the upper part records the early Rupelian stage of the Oligocene, including the Eocene–Oligocene Glacial Maximum at about 33.65 million years ago.

The sedimentology tells its own vivid story. The lower part of the section consists of fine-grained red floodplain deposits, channelized sandstones, and paleosols, representing a broad alluvial plain drained by southward-flowing rivers. Two prominent unconformities punctuate the sequence. The first, marked by an erosional surface cut into a well-developed caliche, records the uplift of the Çiçekdağı anticline to the south, a reorganization of the drainage network, and the birth of a northward-flowing system feeding a new lake in the basin. Above the second unconformity, a striking change appears: the soil carbonates switch from pure calcite to dolomite. Because dolomite typically precipitates in hypersaline settings where evaporation outpaces freshwater input, its arrival signals rising lake salinity and a shift toward markedly drier conditions, a conclusion reinforced by the thick Oligocene evaporite deposits found elsewhere in the Çankırı Basin.

The most striking results come from clumped isotope thermometry, a geochemical technique that measures the tendency of heavy carbon and oxygen isotopes to bond together within carbonate minerals. Because this bonding is temperature-dependent, the abundance of these isotope clumps in pedogenic carbonates, the nodules and caliches that form in ancient soils, provides a direct gauge of the temperature at which the carbonate crystallized. The team analyzed 14 carefully screened samples on a Thermo 253+ mass spectrometer, running ten to twenty replicates per sample across 28 analytical sessions to achieve a repeatability of about 30 parts per million. Petrographic examination confirmed that the carbonates retained their original micritic textures with no evidence of burial recrystallization, and the reconstructed temperatures all fell within plausible Earth-surface values, giving confidence that the primary climate signal had survived.

The temperature record divides cleanly into three phases. In the early to middle Priabonian, soil carbonate formation temperatures averaged a temperate 24.4 degrees Celsius. Then, beginning in the middle Priabonian around 37 million years ago, temperatures jumped by roughly 9 degrees Celsius, with samples between the two unconformities averaging 34 degrees. Finally, above the second unconformity, temperatures fell by about 7 to 8 degrees, settling at an average of 27.4 degrees as the Eocene–Oligocene Glacial Maximum approached. Statistical tests confirmed that all three groups differ significantly. Because soil carbonates in mid-latitude seasonal climates tend to form during warm, dry periods of soil dewatering, the researchers interpret these values as tracking warm-season, or summer, temperatures rather than annual means, a reading consistent with pollen-based temperature estimates from slightly older Lutetian deposits in Anatolia.

The warming phase is the headline discovery. Marine records from the Southern Ocean and the North Atlantic have long hinted at a Late Eocene Warming between about 37.5 and 36.5 million years ago, but this is the first quantitative terrestrial record of the event in western Eurasia. Its cause remains debated: some evidence points to rising atmospheric carbon dioxide late in the Eocene, while other work implicates a reorganization of North Atlantic ocean circulation, including the possible onset of a subtropical gyre or an early version of the Atlantic meridional overturning circulation around 36 million years ago. Crucially, the warming in Anatolia coincided with the first of two aridification steps. Reconstructed soil water oxygen isotope values rose by about 1.7 per mil, a pattern the authors attribute to progressive evaporative enrichment of soil moisture, and a modest rise in carbon isotope values hints at increasing plant water stress. Together, the data sketch a late Eocene Anatolia that was both hotter and drier than before.

The second aridification step, beginning around 35.2 million years ago, is the more consequential one. It coincides with the lake retreat recorded at the second unconformity, spans the Eocene–Oligocene Transition itself, and culminates in the cooling and salinity increase of the earliest Oligocene. Notably, this drying began at least 1.5 million years before the peak of Antarctic glaciation, which means it cannot be a simple consequence of the ice sheet’s growth. Instead, the authors suggest it reflects an earlier, spatially uneven cooling of the North Atlantic, where shifting ocean gyres responding to falling carbon dioxide levels redistributed heat and moisture well before the classic glacial maximum. The lake level drop, in other words, was decoupled from global sea level, pointing to a regional hydroclimatic crisis rather than a glacio-eustatic one.

These climatic swings map onto one of the most famous events in mammalian evolution: the Grande Coupure, the great faunal rupture that saw roughly 55 percent of western Europe’s placental mammal genera go extinct as mammals of Asian origin poured in. The timing is telling. The late Eocene warming and the first aridification step cover the mammalian biohorizons MP18 and MP19, exactly when the first Asia-derived taxa, including the anthracotheriid artiodactyl Elomeryx, the possible gelocid Phaneromeryx, and the amphicyonid carnivoran Cynodictis, trickled through Balkanatolia into western Europe. Environmental stress from heat and drought may have weakened Balkanatolia’s endemic fauna, which all but vanished during the Priabonian, while opening ecological space for Asian newcomers that had been present in the province since the Bartonian. Recent diversification modeling supports the idea that climate stress, rather than direct competition with the invaders, drove the decline of Europe’s native lineages.

Yet the story carries an ironic twist. During the second aridification step and the glacial maximum itself, faunal exchange between Balkanatolia and western Europe appears to have stopped, even though the sea-level fall at the glacial maximum fully connected the western Balkanatolian landmass to western Europe. The authors suggest that the drying and cooling created a persistent environmental barrier across central and southern Europe, one possibly sharpened by orographic effects on precipitation from the rising Alps, that blocked the westward march of Asian mammals until exchanges resumed later in the Rupelian. The last known endemic Balkanatolian mammal, the embrithopod Axainamasia sandersi, clung on until around the transition, showing that some island relics persisted even as their world grew hotter, drier, and then colder. What emerges from the hills of central Anatolia is a portrait of a continent in climatic flux, where successive pulses of warming, drying, and cooling did not merely accompany the fall of one fauna and the rise of another, but actively choreographed it.

Subject of Research: Terrestrial climate change in Anatolia across the Eocene–Oligocene Transition and its role in mammalian dispersal

Article Title: Anatolia (Türkiye) during the late Eocene and the Eocene–Oligocene Transition: successive warming and cooling, aridification, and implications for the westward dispersal of Asian terrestrial mammals

Article References: Botté, P., Licht, A., Jourdan, A.-L., Montheil, L., Demory, F., Kaya, M., Ocakoğlu, F., Akkiraz, M. S., İbilioğlu, D., Coster, P., Métais, G., Raynaud, B., & Beard, K. C. (2026). Anatolia (Türkiye) during the late Eocene and the Eocene–Oligocene Transition: successive warming and cooling, aridification, and implications for the westward dispersal of Asian terrestrial mammals. Climate of the Past, 22(9), 1585-1608. https://doi.org/10.5194/cp-22-1585-2026

Image Credits: AI Generated

DOI: 10.5194/cp-22-1585-2026

Keywords: Eocene–Oligocene Transition, Anatolia, clumped isotope thermometry, paleoclimate, aridification, mammal dispersal, Grande Coupure, Balkanatolia, magnetostratigraphy, pedogenic carbonates, Antarctic glaciation, Climate of the Past

The research team, led by Ayşe Gül Filik and corresponding author Gökhan Filik of the university’s Agricultural Biotechnology Department, together with Olgay Kaan Tekin, set out to answer a question that has become increasingly urgent in modern animal science: can native plant resources rich in bioactive compounds serve as effective, natural alternatives to synthetic feed additives? Consumer pressure for so-called clean label animal products, combined with rising feed costs and concerns over chemical residues, has pushed researchers worldwide to screen local flora for phytogenic additives — plant-derived compounds that might improve animal health and product quality without pharmaceutical inputs. Viburnum opulus, which grows wild across Europe, North Africa, northern Asia, and particularly in the Turkish provinces of Kayseri, Sivas, Tokat, Kırşehir, and Ankara, presented an attractive candidate because of its unusually dense phytochemical profile.

That profile is what makes the fruit scientifically compelling. Analyses of Viburnum opulus berries have revealed high concentrations of polyphenols, flavonoids, tannins, carotenoids, and vitamin C. The dominant phenolic compound is chlorogenic acid, which can account for between 54 and 96 percent of the fruit’s total phenolic content and is regarded as a powerful antioxidant and antimicrobial agent. The fruit is also rich in organic acids, particularly malic and quinic acids, and contains notable concentrations of free amino acids such as aspartic and glutamic acid. Previous laboratory and pharmacological studies have linked Viburnum opulus extracts to lipid metabolism regulation, reductions in free fatty acids, cholesterol homeostasis effects, and even anticancer and antidiabetic activity, but almost none of this work had examined the plant as a direct dietary supplement in poultry. The Turkish team’s experiment was designed to fill that gap with a dose-response approach.

The trial involved 176 laying Japanese quails aged 30 weeks, a species favored in poultry nutrition research for its short generation interval and high egg production capacity. The birds — 132 females and 44 males — were randomly allocated into four dietary treatment groups, each with 11 replicate cages containing three females and one male. The cage, not the individual bird, served as the experimental unit for all performance and production measurements, a design choice that guards against pseudo-replication in statistical analysis. The control group received a standard basal diet formulated to meet quail nutritional requirements with 177 grams per kilogram of crude protein and 2800 kilocalories per kilogram of metabolizable energy. The three treatment groups received the same basal diet supplemented with Viburnum opulus fruit powder, abbreviated VOFP, at inclusion levels of 5, 10, and 15 grams per kilogram of feed. The fruit itself was harvested at full maturity from the university’s research fields, air-dried for a week, finished in a ventilated oven at 65 degrees Celsius for 48 hours, and ground through a one-millimeter sieve in an ultra-centrifuge mill to ensure homogeneous mixing. The feeding experiment ran for eight weeks under a 16:8 light-dark photoperiod with feed and water available ad libitum.

Over the 56-day trial, the researchers tracked body weight, body weight gain, feed intake, and feed conversion ratio weekly, collected eggs twice daily, and subjected eggs gathered on the third day of each week to a battery of quality analyses. External parameters included egg weight, dimensions measured with digital calipers, shape index, shell thickness at three points along the shell, and breaking resistance determined with a texture analyzer. Internal quality was assessed through albumen and yolk heights, albumen and yolk indices, and the Haugh unit, the internationally recognized standard for egg interior quality. Yolk color was quantified spectrophotometrically using CIELAB parameters. Critically, the team also monitored cholesterol metabolism by analyzing yolk cholesterol concentrations at the start of the trial and during weeks two, four, six, and eight, using a spectrophotometric extraction method adapted from earlier phytogenic additive research. Data were analyzed with general linear models, and orthogonal polynomial contrasts were applied to detect dose-response relationships across the supplementation levels.

The headline finding on performance was reassuring: dietary VOFP supplementation produced no statistically significant adverse effects on body weight, body weight gain, or feed conversion ratio, indicating that the birds tolerated even the highest inclusion level well. There were, however, subtle shifts in feeding behavior. Total feed intake was highest in the 5 gram per kilogram group at 7888.0 grams, while the 15 gram per kilogram group consumed the least at 7115.6 grams, a statistically significant difference. The authors suggest this reduction at the highest dose may reflect the fruit’s acidic profile — its abundant malic and quinic acids may slightly inhibit palatability — though the free amino acids in the fruit could simultaneously support protein metabolism. Egg production itself was statistically unchanged across groups, but the 5 gram per kilogram group achieved the highest total egg weight at 1828.60 grams and produced notably more afternoon-laid eggs than the control and highest-dose groups.

The most striking results emerged in egg internal quality. Supplementation at 5 grams per kilogram significantly increased egg yolk height, which reached 13.55 millimeters, and elevated the yolk index compared with controls, both indicators of a richer, more standing yolk. Albumen weight and albumen index were also highest at this dose. Among yolk color parameters, the b* value, which reflects yellowness, peaked at 19.74 in the 10 gram per kilogram group — an attribute with real market value, since consumers associate deeper yolk color with superior eggs. Shell characteristics told a more nuanced story: shell weight decreased with supplementation, reaching its lowest value of 1.22 grams in the 5 gram per kilogram group, yet shell thickness and breaking resistance were unaffected, suggesting that mineral metabolism and structural integrity were preserved even as shell mass shifted. The Haugh unit remained statistically unchanged across all treatments.

The cholesterol results are the most tantalizing and the most cautiously framed. Across the trial, average yolk cholesterol concentrations declined numerically in all supplemented groups, but statistical significance appeared only once: in the sixth week, when cholesterol in the 15 gram per kilogram group fell to 41.04 milligrams per gram of yolk, down from 52.31 milligrams per gram in the control group. The authors interpret this as a potential time-dependent effect of the fruit powder on cholesterol metabolism, plausibly connected to the phenolic compounds that earlier cell studies have linked to lipid accumulation and fatty acid metabolism pathways. Yet they are careful to note that the specific phytochemical composition of the powder used in this trial was not characterized, so the mechanism remains hypothetical rather than confirmed. The transient nature of the effect — significant in week six but not sustained across the full eight weeks — underscores how much remains unknown about how plant bioactives interact with avian physiology over time.

What the study ultimately delivers is preliminary but valuable evidence that Viburnum opulus fruit powder is a viable, well-tolerated phytogenic feed additive for laying quails, with the low dose improving selected internal egg quality traits and the high dose showing a potential, if inconsistent, cholesterol-modulating effect. The researchers call for follow-up work incorporating phytochemical characterization, hepatic cholesterol metabolism markers, antioxidant status measurements, and gut microbiota analyses to pin down the mechanisms at play. They also point to food science findings showing that encapsulation can stabilize the fruit’s bioactive compounds, hinting at strategies to enhance and prolong its effects in feed. For a fruit long celebrated in Anatolian folk tradition and now attracting attention in pharmacology laboratories worldwide, the journey from village juice press to scientific feed supplement is still at its beginning — but these quail eggs offer an early, measurable sign that the berry’s bioactive promise may extend from human health into the food chain itself.

Subject of Research: Effects of dietary Viburnum opulus fruit powder supplementation on performance, egg quality, and yolk cholesterol in laying Japanese quails

Article Title: The effects of Viburnum opulus L. fruit powder on the performance, egg traits, and egg cholesterol of laying Japanese quails

Article References: Filik, A. G., Filik, G., & Tekin, O. K. (2026). The effects of Viburnum opulus L. fruit powder on the performance, egg traits, and egg cholesterol of laying Japanese quails. Archives Animal Breeding, 69(3), 507-515. https://doi.org/10.5194/aab-69-507-2026

Image Credits: AI Generated

DOI: 10.5194/aab-69-507-2026

Keywords: Viburnum opulus, Japanese quail, phytogenic feed additive, egg quality, egg yolk cholesterol, poultry nutrition, chlorogenic acid, clean label, feed conversion ratio, Haugh unit, Anatolia, animal science

The genus Sideritis, a member of the mint family Lamiaceae, comprises dozens of species distributed across the Mediterranean basin, and Turkey is one of the richest centers of diversity for the group. Locally, the dried flowering aerial parts of these plants are steeped as a soothing infusion, often called mountain tea or dağ çayı, and traditionally used to ease digestive complaints, calm colds, and support general wellbeing. Earlier pharmacological work on the genus has documented anti-inflammatory, antioxidant, antimicrobial, and antispasmodic properties, which has fueled growing scientific and commercial interest in these plants. Yet many Anatolian species remain poorly characterized, and distinguishing between closely related taxa can be surprisingly difficult, both for botanists and for the herbal trade that depends on correctly identified raw material.

That identification problem is precisely where the new study makes its most practical contribution. The researchers set out to determine whether specific secondary metabolites, particularly the phenylethanoid glycoside martynoside, could serve as discriminative chemotaxonomic markers, chemical fingerprints that reliably distinguish one species from another. Chemotaxonomy, the use of chemical profiles to classify and authenticate organisms, has become an increasingly valuable tool as global demand for herbal products rises and adulteration or mislabeling of medicinal plants becomes a genuine concern. For endemic species with limited geographic ranges, such as the two Anatolian Sideritis taxa examined here, robust chemical markers could help protect both consumer safety and biodiversity.

To build those fingerprints, the team deployed a two-pronged analytical strategy. First, they characterized the essential oil compositions of both plants using gas chromatography with flame ionization detection and gas chromatography coupled to mass spectrometry, the gold-standard techniques for resolving and identifying volatile compounds. Second, they mapped the non-volatile phenolic constituents using liquid chromatography tandem mass spectrometry, or LC-MS/MS, which allows researchers to detect and tentatively identify polar compounds such as flavonoids and phenylpropanoid glycosides with high sensitivity. The biological potential of the extracts was then evaluated through a battery of standardized antioxidant and antimicrobial assays, allowing the researchers to correlate the chemical findings with measurable functional activity rather than relying on chemistry alone.

The essential oil results revealed two strikingly different volatile worlds. Sideritis syriaca subsp. nusairiensis produced a hydrocarbon-dominated profile, with its most abundant constituents being hexahydrofarnesyl acetone at 11.7 percent, hexadecanoic acid at 11.6 percent, and the long-chain alkane nonacosane at 10.9 percent. This composition translates into the waxy, fatty olfactory notes often associated with cuticle lipids and long-chain molecules. Sideritis argyrea, by contrast, displayed a terpene-rich profile dominated by monoterpenes and sesquiterpenes: beta-pinene at a remarkable 35.5 percent, alpha-pinene at 24.3 percent, and the sesquiterpenoid epi-cubebol at 13.0 percent. Anyone who has walked through a pine forest will recognize the significance of that pinene content, because these compounds are responsible for the fresh, resinous, pine-like aroma that characterizes many coniferous landscapes.

These chemical differences were not merely academic curiosities. The researchers noted that the volatile profiles correlated directly with the olfactory characteristics of the two plants, explaining why the two mountain teas would smell and taste noticeably different despite their close relationship. The waxy and fatty notes of Sideritis syriaca subsp. nusairiensis stand in sharp contrast to the crisp, fresh pine character of Sideritis argyrea. For the herbal tea industry, where aroma is a key driver of consumer preference and product identity, such distinctions carry real economic weight. They also provide a practical means of authentication: a supplier or regulator could, in principle, verify the botanical identity of a batch of dried mountain tea simply by analyzing its volatile profile.

The phenolic analysis added another layer of differentiation. LC-MS/MS identified a higher prevalence of methylated and acylated flavonoid and phenylpropanoid derivatives in Sideritis argyrea compared with its counterpart. Methylation and acylation are biochemical modifications that alter the solubility, stability, and biological behavior of plant phenolics, and their prevalence in one species but not the other reinforces the idea that these two taxa have followed genuinely divergent metabolic paths. Phenylethanoid glycosides such as verbascoside and martynoside, compounds well documented in the Lamiaceae family and studied for their antioxidant and anti-inflammatory properties, form part of this phenolic repertoire and underpin the study’s chemotaxonomic argument.

When the team turned to biological testing, the functional differences between the two species became even more apparent. Sideritis argyrea exhibited more pronounced antioxidant activity, achieving an IC50 value of 0.18 milligrams per milliliter in the standardized assays, and it demonstrated a broader antifungal spectrum, with particularly notable activity against Candida species. The IC50 value, the concentration required to neutralize half of the free radicals in the test system, serves as a widely used benchmark of antioxidant potency, and lower values indicate stronger activity. Candida species are yeasts that include common human pathogens, and the rise of antifungal resistance has made the search for new antifungal compounds from natural sources an urgent priority in medical mycology.

The superior performance of Sideritis argyrea in both antioxidant and antifungal assays aligns neatly with its chemical profile. Terpene-rich essential oils, particularly those abundant in pinenes, are well known for antimicrobial properties, and the elevated levels of modified flavonoids and phenylpropanoids likely contribute additional radical-scavenging capacity. The authors conclude that Sideritis argyrea possesses genuine potential as a source of natural bioactive substances with medicinal interest. At the same time, they are careful to frame their findings within the scope of the investigated populations, a scientifically responsible caveat given that essential oil composition in plants can vary with geography, altitude, harvest time, and environmental conditions.

Beyond the laboratory findings, the study carries broader implications for conservation and commerce. Both taxa are endemic to Anatolia, meaning they grow nowhere else on Earth, and endemic plants with medicinal reputations are often vulnerable to overharvesting as demand grows. Reliable chemotaxonomic markers give researchers and regulators the tools to authenticate plant material, trace supply chains, and support sustainable cultivation initiatives, much as DNA barcoding has been proposed for related Sideritis species destined for industrial cultivation. For now, the message from the Turkish team is clear: the two mountain teas of Anatolia are not interchangeable. One smells of pine and fights microbes with terpene firepower, while the other carries a waxy, fatty signature and a different phenolic arsenal. As interest in functional foods and plant-based therapeutics continues to surge worldwide, studies like this one remind us that the fine chemical details separating closely related plants can determine everything from the flavor in the cup to the future of a species on a mountainside.

Subject of Research: Comparative phytochemistry and biological activities of two endemic Anatolian Sideritis mountain tea species

Article Title: Comparative phytochemical analysis and biological activities of two Anatolian Mountain Teas: Sideritis syriaca subsp. nusairiensis and Sideritis argyrea

Article References: Saltan, N., Iscan, G., Kose, Y. B., Goger, F., & Demirci, B. (2026). Comparative phytochemical analysis and biological activities of two Anatolian Mountain Teas: Sideritis syriaca subsp. nusairiensis and Sideritis argyrea. Plant Biosystems, 160(4), Article 223. https://doi.org/10.1007/s44473-026-00231-4

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00231-4

Keywords: Sideritis, mountain tea, chemotaxonomy, essential oil, GC-MS, LC-MS/MS, antioxidant, antifungal, phenolic compounds, beta-pinene, Anatolia, endemic plants

The team, led by Eren Şahiner of Ankara University’s Earth Sciences Application and Research Center, together with Tamer Koralay, Bilal Söğüt, Tunç Sezgin, and Yusuf Kağan Kadıoğlu, dated five specimens drawn from the Frigidarium’s fabric. Optically stimulated luminescence, or OSL, works by measuring the trapped charge accumulated in mineral grains such as quartz since they were last exposed to sunlight or heat. When a brick is fired or mortar quartz is exposed during preparation, its luminescence clock resets; from that moment, background ionizing radiation from the surrounding sediments, cosmic rays, and the sample’s own radioisotopes steadily winds the clock forward. In the laboratory, controlled optical stimulation releases the stored signal, and the intensity reveals the equivalent dose, the total radiation absorbed since the resetting event. Dividing that dose by the environmental dose rate yields an age.

What distinguishes this study is the rigor of its dose-rate protocol. The researchers documented every step, including grain-size-dependent attenuation of beta radiation, a carbonate water-equivalence correction specifically designed for lime-bound mortars, and an explicit assessment of gamma dose-rate heterogeneity. Lime mortars are notoriously difficult subjects for luminescence dating because their carbonate content alters the way water content and radiation attenuation interact, and the team applied the Carb-style modeling approach to handle this. Gamma dose-rate heterogeneity is a further subtlety: in a wall of compound masonry, where bricks and mortar alternate, the radiation field is not uniform, and a sample’s dose rate depends on the geometry of its immediate surroundings. Rather than treating this uncertainty as a nuisance to be ignored, the authors modeled the gamma-field geometry as a Bayesian nuisance parameter, propagating the dosimetric uncertainty of compound masonry directly into the final chronological posteriors.

The five OSL ages were then synthesized in a constrained Bayesian phase model, a framework adapted from the radiocarbon dating community, carrying only stratigraphic information and terminus post quem priors. In plain terms, the model was told only the relative order of events and the earliest possible dates, and then asked to reconcile the luminescence measurements into coherent phases of the building’s life. Three phases emerged. Primary construction of the Frigidarium falls in the late first to early second century CE, with a posterior median of 162 CE and a 95.4 percent highest-posterior-density interval spanning 60 to 323 CE. This is consistent with the flourishing of Roman bath architecture in Caria during the Antonine and Severan periods, when cities of western Anatolia competed to monumentalize their civic centers.

The second phase captures a repair episode, dated with a mode of 375 CE within an interval of 365 to 499 CE. The coincidence is striking: the great Eastern Mediterranean earthquake of 365 CE, generated near Crete and felt across the entire region, devastated coastal cities and is one of the most extensively documented seismic events of antiquity. The repair date aligns closely with that catastrophe, suggesting that the Frigidarium was damaged and subsequently restored in its aftermath. Archaeoseismology, the discipline that reads earthquake damage in ancient structures, has long catalogued tilted walls, displaced masonry blocks, and collapsed colonnades across the Mediterranean, but assigning absolute dates to such damage has remained difficult. Here, the luminescence clock provides an independent chronological anchor for a restoration that historical sources alone could never have pinned to this provincial city.

The third phase concerns the building’s terminal collapse. Under dosimetric priors alone, the model placed the collapse at a mode of 545 CE within a broad window of 405 to 802 CE, a range too wide to discriminate among the known seismic events of the period. The Eastern Mediterranean experienced what some scholars describe as seismic clustering between the fourth and sixth centuries, with major earthquakes in 494 CE and in 554 to 558 CE, as well as events around 610 to 630 CE. Any of these could, in principle, have delivered the fatal blow. The Bayesian model alone could not choose between them, and the authors were careful not to overstate what the luminescence data could resolve.

The decisive breakthrough came from archaeology rather than physics. Coins minted in 613 CE were found sealed beneath the collapse debris, providing a hard terminus post quem: the building could not have fallen before those coins were deposited. When this numismatic evidence was incorporated into the Bayesian model, the collapse window narrowed dramatically to 613 to 850 CE, with a mode of 633 CE. Within that refined window, the circa 610 to 630 CE seismic anchor dominates, achieving an overlap probability of 0.31 at a 25-year tolerance. The statistical conclusion is that a seismic trigger is the most probable cause of the terminal loss of the Frigidarium’s monumental function in the early seventh century CE, a period of chronic instability for the Eastern Roman Empire marked by Persian wars, plague, and persistent tectonic activity in western Anatolia.

Stratonikeia itself is an ideal laboratory for such work. Located in the Yatağan district of Muğla Province, the city has been the focus of long-running excavations directed from Pamukkale University, and previous studies have documented earthquake relics in the ancient city and at the nearby sanctuary of Hekate at Lagina. Earlier archaeometric investigations of Stratonikeia’s bricks, mortars, and building stones, including luminescence dating of bricks from the Erikli Basilica and characterization of the theater’s architectural stones, laid the groundwork for the present study. The Frigidarium, the cold room where bathers began or ended their circuit of the Roman baths, is a structurally massive space whose thick walls preserve a legible record of construction, repair, and destruction.

The methodological implications extend well beyond one building. Mortar dating by luminescence has matured over the past two decades, and reviews of the field have emphasized the need for transparent, reproducible dose-rate assessment, particularly for carbonate-rich materials. By publishing a fully documented protocol, treating gamma-field geometry as an explicit model parameter, and releasing the R and Python scripts implementing the dose-rate calculation, equivalent-dose modeling, and Bayesian phase chronology, together with full Monte Carlo posterior samples, the team has set a benchmark for how archaeoseismic chronologies should be constructed and reported. The approach converts scattered, imprecise age estimates into a coherent probabilistic narrative of a building’s biography.

For the wider public, the study offers something rare: a precise, quantified answer to the question of when a great Roman monument was born, when it was wounded, and when it died. The Frigidarium of Stratonikeia rose in the high empire, was patched after the great earthquake of 365 CE, and stood for roughly another two and a half centuries before an early seventh-century tremor ended its life as a functioning bath. In the layered ruins of Caria, the marriage of luminescence physics and Bayesian statistics is now capable of reading that biography directly from the walls themselves, giving voice to buildings that survived their own civilization by more than a millennium.

Subject of Research: Bayesian archaeoseismic chronology of the Stratonikeia Frigidarium using optically stimulated luminescence dating

Article Title: Bayesian archaeoseismic chronology of the Stratonikeia Frigidarium from construction to seismic collapse

Article References: Şahiner, E., Koralay, T., Söğüt, B., Sezgin, T., & Kadıoğlu, Y. K. (2026). Bayesian archaeoseismic chronology of the Stratonikeia Frigidarium from construction to seismic collapse. Archaeological and Anthropological Sciences, 18(10), Article 203. https://doi.org/10.1007/s12520-026-02564-9

Image Credits: AI Generated

DOI: 10.1007/s12520-026-02564-9

Keywords: luminescence dating, OSL, Stratonikeia, archaeoseismology, Bayesian modelling, Roman architecture, frigidarium, Roman baths, earthquake chronology, mortar dating, Anatolia, 365 CE earthquake