Temporal and spatial variation in radiocarbon (14C) in the atmosphere has been the subject of investigation from the first pioneering work of Libby and Arnold. However, as the precision of measurements has improved, now by almost two orders of magnitude, what constitutes a significant variation has also changed. Furthermore, it has become possible to test degrees of variation over much longer timescales and with ever wider geographic coverage. As knowledge has improved, the interpretation of 14C measurements has had to be revised. These re-evaluations, and the loss of chronological precision that comes with accurate calibration, have often been seen as an unfortunate drawback in the 14C dating method. However, these problems have stimulated extensive research in global 14C records, statistical methods for dealing with complex 14C data, and measurement methods. This research has provided a wealth of information useful for other scientific challenges, most notably the quantification of the global carbon cycle, but also enabled, in the right circumstances, measurement precision an order of magnitude better than if there had been no variation in atmospheric 14C. Challenges remain but the research undertaken for 14C calibration has, through its ingenuity and innovation, provided rich scientific dividends in both chronology and broader geoscience.

Direct accelerator mass spectrometry (AMS) dating is crucial for a correct integration of plant remains in the (pre)history of crops, particularly for those that do not belong to the Neolithic package and are known to arrive in Europe much later. This paper reviews one of the earliest records of rye from Romania. The grains were discovered in the tell settlement of Cunești, which belongs to the Gumelnița communities (ca. 4600–3900 BC). In 1954, due to Danube flooding, a large portion of the south part of the tell collapsed, and between the burnt dwelling visible in the resulting profile, a large number of sherds from three typical Gumelnița pots were identified. According to the excavation’s author, rye grains were found in association with those sherds, and it was assumed that a batch was stored in these Eneolithic vessels. Consequently, the rye was published as belonging to the Gumelnița period. Our reanalysis led to two radiocarbon (14C) dates, from two different laboratories, which indicate that the Cunești rye is not prehistoric but dates to the medieval period. To correct this error concerning this rye batch and the implications for European archaeology, we decided to republish these grains in an updated chronological framework. In addition, we performed stable isotope analyses on the charred grains, confirming they were cultivated on dry land, as well as a 3D morphometric investigation. Our research brings new and original data on rye cultures from the medieval period in southeastern Europe.

Food production is one of the most significant achievements in Andean history. The domestication of plants and animals presented an enormous challenge, relating to changing technologies, settlement patterns, and social organization. This paper aims to assess Atacama Desert population dynamics and their relationship to the domestication of plants and animals through chronological modeling using kernel density estimation on radiocarbon (14C) dates, assuming that a higher 14C probability density is related to more intense human occupation. The analysis is based on a 14C dataset comprising 1003 14C dates (between 11,000 and 150 BP) from 243 archaeological sites in the Arica and Tarapacá regions of northern Chile, collected from published data. We observed two population-dynamics inflection points for these regions. First, starting at ca. 3000 BP, constant population growth occurred, which was related to horticulture in the Arica region and to agriculture in the Tarapacá region. Second, between ca. 1000 and 400 BP, a general population rise occurred due to the consolidation of intensive agriculture in the lowlands and precordillera altitudinal belts in both regions and the integration of the coast and the altiplano into macro-regional population dynamics.

An archaeological excavation conducted on U Kasáren St. in the Prague Castle area (Czech Republic) in 2020 revealed the remains of a medieval settlement consisting of houses of different constructions (pit dwelling, masonry construction), pyrotechnical (possibly metallurgical) features and unspecified pits. The excavation also revealed evidence of fire events and traces of viniculture on the outskirts of the Prague Castle area. Archaeological data allowed only a rough dating of the investigated settlement in the 10th–13th centuries. This paper presents the results of the radiocarbon dating of various materials (animal bones, archaeobotanical samples) from the settlement features and the contribution of the results to the clarification of the chronology of the site.

Single-year 14C sampling of a spruce log from the timber platform on which the Āraiši lake-fortress was built dates this timber exactly, by synchronization with AD 774/5 Miyake event. Dendrochronological synchronisms between the dated log and other timbers provide annual precision for the construction of the site. The felling date obtained, AD 835, is 50–60 years later than that proposed previously (Meadows and Zunde 2014) on the basis of a wiggle-match between 14C ages of decadal blocks and the IntCal13 calibration curve (Reimer et al. 2013), although the same 14C data favor a felling date in the AD 830s when wiggle-matched to IntCal20 (Reimer et al. 2020). Our results appear to confirm doubts expressed by Philippsen et al. (2022) about IntCal20 values from ca. AD 825-835.

Accelerator mass spectrometry radiocarbon (AMS 14C) dates (n = 78) from human bone collagen were analyzed in the largest high-resolution chronology study to date at the ancient city of Teotihuacan in central Mexico (ca. AD 1–550). Samples originate from the residential neighborhood of La Ventilla, located in the heart of this major urban center. Here, a trapezoidal model using Bayesian statistics is built from 14C dates combined with data derived from the stylistic analysis of ceramics from burial contexts. Based on this model, we suggest possible refinements to Teotihuacan’s ceramic chronology, at least within the La Ventilla neighborhood. We also explore the abandonment and reoccupation of La Ventilla after the political collapse of Teotihuacan in the Metepec and Coyotlatelco phases. Findings suggest that these ceramic phases began earlier than is currently projected and that the well-documented abandonment period of La Ventilla may have occurred more abruptly than originally estimated.

Absolute dating of plasters and mortars clearly represents a key information to study important structures and buildings that may have undergone a difficult story starting from their construction. This is for instance the case of the architectures in the archaeological site of Hierapolis (Denizli, Turkey). However, when discussing about the possibility to apply radiocarbon (14C) dating, in this site the presence of different sources of contaminants, due to the geological and geochemical conditions and to the used raw materials, prevents the binder dating. As an alternative, we thus decided to focus on the small fragments of straw that had been used as additives in the mortar/plaster matrices. The fragments were identified, selected and dated using a 14C experimental set-up specifically optimized for microgram-sized samples. The obtained results were satisfying, even though the measured 14C ages also pointed out some possible criticalities in dating such small samples collected from a carbonaceous matrix.

Regional offsets from Northern Hemisphere radiocarbon (14C) calibration curves are widely recognized for monsoon Asia and often hinder accurate 14C dating. In this paper, we explore the possible linkage between summer monsoon intensity and 14C offsets using tree-ring δ18O and 14C data from Thailand. We developed a 297-yr floating tree-ring δ18O chronology comprising seven teak log-coffin samples from the Ban Rai rock shelter site, northwestern Thailand. The outermost ring of our chronology was estimated to date from 358–383 CE, within a 95.4% (2σ) probability range, based on a total of 10 14C measurements that were wiggle-matched against a mixed calibration curve evenly weighted from the IntCal20 and SHCal20 curves. Backward trajectory analysis showed that an intensified (weakened) summer monsoon detected in a modern tree-ring δ18O chronology was most likely to be induced by increased (decreased) air mass transport from the tropical Indian Ocean, which is an area of intense upwelling where the 14C concentration is lower than the atmospheric 14C level. However, partly because of the limited sample size and dating uncertainty, the direct linkage between the tree-ring δ18O series and 14C records obtained from our teak log-coffin samples could not be statistically verified.

This study focuses on the chronology of King Den’s reign, the fifth ruler of the 1st Egyptian dynasty. A series of radiocarbon (14C) dates were established on archaeological material from several tombs at the Abu Rawash site, near Cairo, which comprises a complex of 12 monumental mud-brick mastabas. Modeling the 14C results enables us to estimate the date of King’s accession and to link this to the beginning of the 3rd Dynasty, i.e., to Egyptian state’s structuration. Through the application of OxCal software, sets of 14C results obtained from the same archaeological context have been summarized and compared with the precise state of our knowledge on the historical duration of this reign. These results place King Den’s accession between 3104 and 2913 BCE (2σ), with the more likely date being 3011–2921 BCE (1σ). The modeled temporal density thus obtained is based both on new contextualized 14C dates and on an updated reading of the historical information on his reign. This is a dynamic result, which can be refined as soon as we have more data to integrate into the model. Above all, this resulting model becomes a crucial chronological point to better determine the beginning of the Egyptian Old Kingdom.

Radiocarbon observations (Δ14C) in dissolved inorganic carbon (DIC) of seawater provide useful information about ocean carbon cycling and ocean circulation. To deliver high-quality observations, the Laboratory of Ion Beam Physics (LIP) at ETH-Zurich developed a new simplified method allowing the rapid analysis of radiocarbon in DIC of small seawater samples, which is continually assessed by following internal quality controls. However, a comparison with externally produced 14C measurements to better establish an equivalency between methods was still missing. Here, we make the first intercomparison with the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility based on 14 duplicate seawater samples collected in 2020. We also compare with prior deep-water observations from the 1970s to 1990s. The results show a very good agreement in both comparisons. The mean Δ14C of 12 duplicate samples measured by LIP and NOSAMS were statistically identical within one sigma uncertainty while two other duplicate samples agreed within two sigma. Based on this small number of duplicate samples, LIP values appear to be slightly lower than the NOSAMS values, but more measurements will be needed for confirmation. We also comment on storage and preservation techniques used in this study, including the freezing of samples collected in foil bags.

Past human population dynamics play a key role in integrated models of understanding socio-ecological change over time. However, little analysis on this issue has been carried out for the prehistoric societies in the Lower Danube and Eastern Balkans area. Here, we use summed probability distributions of radiocarbon dates to investigate potential regional and local variation population dynamics. Our study adopts a formal model-testing approach to the fifth millennium BC archaeological radiocarbon record, performing a region-wide, comparative analysis of the demographic trajectories of the area along lower Danube River. We follow the current framework of theoretical models of population growth and perform global and regional significance and spatial permutation tests on the data. Specifically, we investigate whether populations on both sides of the Danube follow a logistic pattern of steady growth, followed by a major decline over time. Finally, our analysis of local-scale growth investigates whether considerable heterogeneity or homogeneity within the region may be observed over the time span considered here. The results show both similarities and differences in the population trends across the area. Our findings are showcased in relation to the cultural characteristics of the region’s 5th millennium BC societies, and future research directions are also suggested.

Previous research on the Neolithic cist graves of the Western Alpine region—also known under the term Chamblandes type graves—mostly focused on sites located in western Switzerland and eastern France. For the adjacent Aosta Valley (Italy), only a little information is available. Within the framework of our research project, it was possible to identify about 120 stone cist graves from 10 sites in the Aosta Valley. Due to the lack of distinctive grave goods and missing absolute dating, however, their chronological position has been unclear until now. Here we present the first extensive series of radiocarbon dates from Neolithic stone cist graves of the Aosta Valley. We analyzed 31 human bone samples from four sites, and most dates indicate an unexpected early chronological position around the first half of the 5th millennium BCE, in particular, the site of Villeneuve, dating to 4800–4550 cal BCE. This identifies these burials from the Aosta Valley as belonging to the oldest known Neolithic cist graves of the Western Alpine region discovered so far. Altogether, our study provides new evidence allowing the first time to clarify the chronology of these sites and trace the evolution of this burial practice in the Western Alps.

The method of determining the biobased carbon content in liquid fuel samples is standardized, but different laboratories use different protocols during sample preparation and perform the measurements using different machines. The accelerator mass spectrometry (AMS) laboratories use different combustion, preparation, and graphitization methods for the graphite production for the spectrometric measurements. As a result, the intercomparison between the laboratories is inevitable to prove precision and accuracy and to demonstrate that the results are comparable. In this study, we present the results of an intercomparison campaign involving three 14C accelerator mass spectrometry laboratories. Five samples were used in the measurement campaign, including two biocomponents (fatty acid methyl ester, hydrotreated vegetable oil), one fossil component (fossil diesel), and two blends (mixtures of fossil and biocomponent with 90–10% mixing ratio) in the laboratories of CEDAD (Italy), ETH (Switzerland), and INTERACT (Hungary). The results presented by the laboratories are comparable, and all three laboratories could determine the biobased carbon content of the samples within 1% relative uncertainty, which is acceptable in the scientific, economic, and industrial fields for biocomponent determination.

We present a timeseries of 14CO2 for the period 1910–2021 recorded by annual plants collected in the southwestern United States, centered near Flagstaff, Arizona. This timeseries is dominated by five commonly occurring annual plant species in the region, which is considered broadly representative of the southern Colorado Plateau. Most samples (1910–2015) were previously archived herbarium specimens, with additional samples harvested from field experiments in 2015–2021. We used this novel timeseries to develop a smoothed local record with uncertainties for “bomb spike” 14C dating of recent terrestrial organic matter. Our results highlight the potential importance of local records, as we document a delayed arrival of the 1963–1964 bomb spike peak, lower values in the 1980s, and elevated values in the last decade in comparison to the most current Northern Hemisphere Zone 2 record. It is impossible to retroactively collect atmospheric samples, but archived annual plants serve as faithful scribes: samples from herbaria around the Earth may be an under-utilized resource to improve understanding of the modern carbon cycle.

The Single Stage AMS radiocarbon facility at the Australian National University has operated for the past 14 years. This paper presents the pretreatment methods used for the major sample types dated and reflects on whether quality assurance protocols can adequately detect altered materials. The majority of fossil samples dated by the facility are from tropical and arid environments where diagenesis of both organic samples and carbonates is often severe. A large proportion of the samples submitted cannot be dated, and screening and quality assurance methods are crucial. Based on analysis of 250 measurements on bone collagen, quality assurance indicators for bone are revised. From May 2021, the laboratory has accepted dates on collagen where yield >0.5%, %C is in the range of 39.7–46.9, and the C:N ratio is between 3.00 and 3.30.

This article discusses radiocarbon dating results of documents preserved at the Central Library of the University of Tehran (hereafter, CLUT) as part of the project “Irankoran.” The paper adds new evidence to an ongoing campaign of dating Qurʾāns and Oriental manuscripts by the Corpus Coranicum Project. The dated manuscripts include one kūfī fragment of the Qurʾān on parchment (no. 10950) and a selection of Islamic and Persian manuscripts, all from the second millennium: the Arabic dictionary Muǧmal al-Luġah (Meškāt no. 203), the medical encyclopedia Ḏaḫīrah-ye Kh w ārazmšāhī (no. 5156), the epic Panǧ Ganǧ of Neẓāmī (no. 5179), the book of wisdom Ādāb al-Falāsifah (no. 2165) attributed to Ḥunayn b. Isḥāq (d. 873 CE), and one of the oldest extant manuscripts of the Avesta Wīdēwdād (no. 11263). Although the authenticity of their colophons is disputed, radiocarbon dating supports the dates of the colophons; even in cases where they were suspected of being tampered with, they most likely present the accurate original dates of the corresponding manuscripts. Only in the case of Ādāb al-Falāsifah (no. 2165), radiocarbon dating of the parchment has identified the manuscript as non-authentic. Inconsistent carbon dating results of two samples taken from Ḏaḫīrah-ye Khwārazmšāhī (no. 5156) and Panǧ Ganǧ (no. 5179) provide evidence of later replaced/added leaves.

We evaluate carbonate gastropod shells as 14C proxies for groundwater discharge at springs. Groundwater 14C is commonly used to estimate groundwater transit times, and a carbonate shell proxy would present a different way of collecting groundwater 14C data. Specifically, we test the hypothesis that in exclusively groundwater-fed spring systems, water 14C is preserved in carbonate shells at multiple sites, species, and water 14C. We first present isotopic and water temperature variability over several years at three spring sites in Utah. We then compare the 14C of contemporaneously collected water, sediment, and shells of benthic gastropods (Melanoides tuberculata, Pyrgulopsis pilsbryana, and Physella gyrina). We show that water and shell 14C activities at each site are correlated (slope = 1.00, R2 = 0.999, n = 22). These results support the hypothesis that 14C from groundwater is preserved in carbonate shells, and that aqueous gastropods a viable groundwater 14C proxy. Finally, we describe the utility and limitations of using gastropod shells as a groundwater 14C proxy.

A set (n = 37) of new human bone radiocarbon accelerator mass spectrometry (14C AMS) dates from 11 Lithuanian Late Roman Period–Migration Period cemeteries is presented and discussed in the light of the established schemes of archaeological chronology. The focus of the paper is on the burials of the military and social elite, which indicate the emergence of new cultural traditions in E–S and W–Central Lithuania or the immigration that took place during this time. The 14C dates allow us to suggest corrections to the dominant chronological pattern of cultural development in the region.

The Final Neolithic and the Bronze Age (3000–800 BC) are periods of great transformations in the communities inhabiting the area of modern-day Belgium, as testified by archaeological evidence showing an increasing complexity in social structure, technological transformations, and large-scale contacts. By combining 599 available radiocarbon dates with 88 new 14C dates from 23 from funerary sites, this paper uses kernel density estimates to model the temporality in the use of inhumation vs. cremation burials, cremation deposits in barrows vs. flat graves, and cremation grave types. Additionally, by including 78 dates from settlements, changes in population dynamics were reconstructed. The results suggest a phase of demographic contraction around ca. 2200–1800 BC highlighted by a lack of dates from both settlements and funerary contexts, followed by an increase in the Middle Bronze Age, with the coexistence of cremation deposits in barrows and, in a lower number, in flat graves. At the end of the 14th–13th century BC, an episode of cultural change with the almost generalized use of flat graves over barrows is observed. Regional differentiations in the funerary practices and the simultaneous use of different grave types characterize the Late Bronze Age.

Reliable radiocarbon (14C) ages of foraminifera are a prerequisite to generate robust high-resolution age-depth models or to obtain precise understanding of past carbon cycle dynamics. With the advance of small-scale 14C measurements, instrumental precision and levels of contamination (extraneous carbon introduced during sample pretreatment or analysis) became increasingly important to consider. To reduce the effect of carbon contamination, an attempt can be made to remove it by leaching the surface with weak acids. Alternatively, mathematical corrections (e.g., subtraction) based on processing blanks can be applied. We report on 14C analyses of monospecific foraminifera samples compared between different blank corrections (correction against 14C-free CO2, IAEA-C1 and foraminifera) and sample treatments (i) to examine whether chemical pretreatment and mathematical blank subtraction are comparable, and (ii) to determine limitations hindering reliable 14C dating with ever smaller sample sizes. The data show that chemical pretreatment of foraminifera corrected against IAEA-C1 does remove surface contamination and that the same effect can be achieved for untreated samples that were mathematically corrected for blank values determined from sample size-matched 14C-free foraminifera. Leaching only has a beneficial effect on 14C data for older samples, where the isotopic difference between untreated and chemically pretreated samples exceeds the analytical precision.