GIRI (Glasgow International Radiocarbon Intercomparison) was designed to meet a number of objectives, including to provide an independent assessment of the analytical quality of the laboratory/measurement and an opportunity for a laboratory to participate and improve (if needed). The principles in the design of GIRI were to provide the following: (a) a series of unrelated individual samples, spanning the dating age range, (b) linked samples to earlier intercomparisons to allow traceability, (c) known age samples, to allow independent accuracy checks, (d) a small number of duplicates, to allow independent estimation of laboratory uncertainty, and (e) two categories of samples—bulk and individual—to support laboratory investigation of variability. All of the GIRI samples are natural (wood, peat, and grain), some are known age, and overall their age spans approx. >40,000 years BP to modern. The complete list of sample materials includes humic acid, whalebone, grain, single ring dendro-dated samples, dendro-dated wood samples spanning a number of rings (e.g., 10 rings), background and near background samples of bone and wood. We present an overview of the results received and preliminary consensus values for the samples supporting a more in-depth evaluation of laboratory performance and variability.

The fifth season of excavations of Oponice Castle in 2020 was located in the lower castle’s courtyard. The research led to discovery of an original clay floor being heavily burned with charred plank and a rectangular stone-brick construction. The construction has collapsed upper part with a fallen low brick arch. The whole area was covered with numerous stove tiles and one clay mold for the production of stove tiles. The construction was identified as a pottery kiln dated to the second half of the 16th until the first half of the 17th century AD by the findings from excavated layer identified to the kiln destruction. Also, written sources mention a large fire in 1645 which destroyed the castle. The aim of this article is to use different methods of dating and refine the chronology of the context through microarchaeology and Bayesian modeling. For these purposes different types of samples were collected. The sampling focused on site formation process determination of pottery kiln use and the way of its destruction. Applying Bayesian analysis improved overall dating, through modeled time interval of the three individual sequences and helped recreated historical events during the period, when the calibration curve fluctuates.

This research aims to contribute to our knowledge of the chronology of the main cultural entities of the Bronze Age in the Southern Urals. The objectives of this work include the verification of earlier conclusions regarding individual sites, expanding the date series for the key cultures with reliable dates, and creating reference series for the Bayesian modeling of key archaeological sites. Thirty-two samples were selected from reliable contexts. They reflect seven different cultural traditions of the 2nd millennium calBC (Sintashta, Srubnaya, Alakul, Fedorovka, Cherkaskul, Final Bronze Age1, Transition to Early Iron Age2). Collagen (human and domestic animal bones), charcoal, and wood samples were used for radiocarbon dating. Pairs of different-type samples (human bone – animal bone, animal bone – charcoal) were obtained for the same undisturbed burial and the building floor at the time of its abandonment. The data and the composition of δ15N and δ13C isotopes allow the new dates to be considered reliable. Furthermore, the new results do not conflict with the previously obtained accelerator mass spectrometry (AMS) dates. Determining boundary intervals for the main cultures of the Andronovo cultural community (Alakul and Fedorovka) resulted in statistically reliable conclusions on their relationship. The Alakul culture appeared earlier than the Fedorovka culture. The latter has a migratory origin in the Southern Urals. The two traditions have a long history of interaction, but the Alakul culture ending earlier. The series of dates for the Final Bronze Age, divided into two sub-periods, has been significantly expanded. Bayesian modeling of the chronology of the stratified settlement Sintashta II (Levoberezhnoe) made it possible to determine the intervals of the main phases of its history: 2004–1852 calBC (Sintashta culture) and 1410–1170 calBC (Final Bronze Age). Intermediate Cherkaskul phase is represented by a single date (1731–1541 cal BC).

The IntCal family of radiocarbon (14C) calibration curves is based on research spanning more than three decades. The IntCal group have collated the 14C and calendar age data (mostly derived from primary publications with other types of data and meta-data) and, since 2010, made them available for other sorts of analysis through an open-access database. This has ensured transparency in terms of the data used in the construction of the ratified calibration curves. As the IntCal database expands, work is underway to facilitate best practice for new data submissions, make more of the associated metadata available in a structured form, and help those wishing to process the data with programming languages such as R, Python, and MATLAB. The data and metadata are complex because of the range of different types of archives. A restructured interface, based on the “IntChron” open-access data model, includes tools which allow the data to be plotted and compared without the need for export. The intention is to include complementary information which can be used alongside the main 14C series to provide new insights into the global carbon cycle, as well as facilitating access to the data for other research applications. Overall, this work aims to streamline the generation of new calibration curves.

Nitra-Lupka is an important site from the Great Moravian period in Slovakia. A fortified hillfort which was supposed to be from this period, a battery of pottery kilns, and an Early Medieval cemetery were found on the site and researched during 1959–1975. Further, a few small-range excavations took place on the site at the beginning of the 21st century. At the same time, the dating of the hillfort to the Early Medieval period has begun to be questioned. There was also a problem with the localization of settlement that would belong to the battery of pottery kilns. The settlement was discovered recently in 2021 during development-led excavations at Nitra-Šindolka. It was found at the place of the construction of the ecoduct. Two ovens and four other features with numerous ceramics and other findings were discovered. Some of the bones (phalanges of cattle and goat/sheep) were dated by radiocarbon dating being the first 14C data obtained from this site and therefore of high importance for its precise dating.

The Laboratoire des Sciences du Climat et de l’Environnement (LSCE) has operated a radiocarbon dating laboratory for almost 70 years. It has evolved from a traditional ß-decay counting to an accelerator mass spectrometry facility. In 2015, the LSCE received a major upgrade with the installation of a MICADAS. This evolution required adjustments in sample preparation to match the new capability to date samples as small as a few tens of µgC. We summarize here the sample cleaning procedures and the chemical purification or extraction treatment that we apply to the samples. We also report values of blank and reference materials of different matrices that match the large diversity of samples handled at LSCE.

We present the results of a multifaceted study of an antiphonary—liturgical song book—presumably made in Venice in 1607, now in the Ringve, National Music Museum of Norway in Trondheim1. The book is hand-sewn on raised cords, bound in full leather on cardboard covers, originally with metal clamps. The paper block consists of pages printed in black and red that include both song texts and music scores. The red ink is based on vermillion and red lead while the black ink is carbon based. The treads and cords were made of flax. The leather used was made from goat skin. Radiocarbon results confirmed the printing date. The antiphonary shows several signs of repair including the possibility of re-binding. Animal-based glue was used for the repairs as well as for the sizing of both original and repair paper. Two potential periods were identified for reparations, 1670–1710 AD and 1782–1830 AD. This case study was conducted prior to the opening of a new permanent exhibition, Soundtracks, at the Ringve Museum where the book is displayed.

Short-term fluctuations in atmospheric radiocarbon (14C) concentration mark the tree-ring record for the last ∼15 kyr. Terrestrial macrofossils from sediment cores of Lake Suigetsu, Japan, extend this record of fluctuations back to >35 cal ka BP. Their significance, however, is under debate since the signal-to-noise ratio of the Suigetsu record is low and progressively decreases with increasing age. Coherent semi-millennial-scale structures of the Suigetsu 14C record have nevertheless been identified by three different techniques, namely visual inspection, analyses of the first derivative of 14C vs. calendar age, and Bayesian spline inflections of 14C concentration vs. calendar age, and hence appear objectively real. These 14C fluctuations correlate closely with those of the tree-ring-based 14C master record ∼10–14 cal ka. Thus, Suigetsu fine structures attain global significance and may properly reflect atmospheric 14C variability back to ∼35 cal ka. Carbonate-based 14C records from speleothems and ocean sediments are far smoother and form, together with Suigetsu and other data, the backbone of the IntCal20 record >14 cal ka that largely lacks the Suigetsu fine structure. 14C decay reduces 14C-signal amplitudes over time, so Holocene-style 14C signals of solar modulation disappear in the noise beyond ∼10 cal ka. The remaining older 14C fine structures had larger forcings, most likely linked to climate and carbon cycle, especially ocean-atmosphere CO2 exchange, and thus contain valuable information about these factors. They may also provide global stratigraphic tie points to correlate 14C records of oceanic plankton sediments and climate signals independent of problems with local 14C reservoir effects.

Compared with nitrogen and argon, helium is lighter and can better reduce the beam loss caused by angular scattering during beam transmission. The molecular dissociation cross-section in helium is high and stable at low energies, which makes helium the prevalent stripping gas in low-energy accelerator mass spectrometry (AMS). To study the stripping behavior of 14C ions in helium at low energies, the charge state distributions of carbon ion beams with −1, +1, +2, +3, and +4 charge states were measured at energies of 70–220 keV with a compact 14C-AMS at Guangxi Normal University (GXNU). The experimental data were used to analyze the stripping characteristics of C-He in the energy range of 70–220 keV, and new charge state yields and exchange cross-sections in C-He were obtained at energies of 70–220 keV.

Dating organic inclusions in mortars such as charcoals is a useful alternative or complementary method to dating mortars themselves, helping to estimate the building age. To assess the limitations of this dating approach, organic inclusions were searched for in surface mortar layers of six early to late medieval buildings in the Czech Republic with relatively well-known age. Altogether, 123 samples were found. About 80% were successfully radiocarbon (14C) dated. However, only 66% originated from wood relatively young when used in lime burning. To judge which samples are relevant to the actual building date, sufficient statistics is crucial. We recommend dating at least 5–10 samples, i.e., collecting 6–12 samples, for a site with uncomplicated building history, or per building phase. Otherwise, unrealistically old or young dates might be obtained. With the recommended statistics, inclusion-based dating provides building ages with uncertainty of 50–100 years.

In two forensic cases, radiocarbon (14C) bomb-pulse datings of human bones have been performed and analyzed using detailed models to correct for collagen-carbon turnover rates and reservoir effects. The modeled corrections are discussed and the resulting 14C ages compared to later information on actual time of birth and death of the individuals. Simple time lag corrections of bone dates are found to be inadequate, whereas modeling based on age dependent turnover rates and bomb-pulse levels through life combined with substantial reservoir age corrections can explain the observed 14C results.

Nowadays, most radiocarbon (14C) laboratories can reliably avoid and remove any possible sample contamination during the pretreatment of organic samples (e.g., bones, charcoal, or trees) thanks to a series of methods commonly used by the radiocarbon community. However, what about the final step, the storage of graphite? Rarely do the laboratories produce their graphite and ship it as pressed targets to accelerator mass spectrometry (AMS) facilities for measurement. Pressed graphite in aluminum targets are vulnerable to contamination, and during shipment or storage, exogenous carbon can be introduced again. Here we report a test on various archaeological sample materials from different environments and different periods (from the past three millennia to the Middle Paleolithic period). We transformed them into graphite, pressed the graphite into targets and sent them to two different AMS laboratories to be dated. We observe that packing details of the targets, extended shipment and storage time may lead to contamination which can be avoided by appropriate packaging in tight metal cans and sealed in vacuum bags. Close cooperation and coordination between our chemistry laboratory and the AMS facilities, high standards in contamination removal, and efficient measurement planning enabled us to obtain reliable 14C ages within a short time.

The SUERC Radiocarbon Laboratory reports approximately 3000 unknown samples per year with an additional 1200 samples processed for quality assurance purposes. In addition to the primary OxII standard (SRM-4990C) required for AMS batch normalization, secondary “known-age” standards have been used over many years to evaluate individual batch quality. These have included wood (as prepared alpha-cellulose), barley mash, humic acid, a background mammoth bone, known-age bones, and a whisky sample. In this paper, we present some of the results gathered over routine laboratory operation (for more than 10 years) and examine the results illustrating how they are being used to monitor and quality assure performance. Since many of these samples have also been used in the Glasgow intercomparisons, we will also reflect on the results, as well as the actual and potential uses of such samples.

A single-stage accelerator mass spectrometer (GXNU-AMS) developed for radiocarbon and tritium measurements was installed and commissioned at Guangxi Normal University in 2017. After several years of operational and methodological upgrades, its performance has been continuously improved and applied in multidisciplinary fields. Currently, the measurement sensitivity for radiocarbon and tritium is 14C/12C ∼ (3.14 ± 0.05) ×10–15 and 3H/1H ∼ (1.23 ± 0.17)×10–16, respectively, and the measurement accuracy is ∼0.6%, which can meet the measurement requirements in the nuclear, earth, environmental and life science fields. This study presents the performance characteristics of GXNU-AMS and several interesting application studies.

Although paleomagnetic secular variations (PSV) often corroborate radiocarbon (14C)-based lacustrine sediment chronologies, this is not the case at the high-altitude site Khar Nuur in the Mongolian Altai Mountains. Our results show that the inclination pattern resembles those from a regional reference record from Shireet Naiman Nuur and global geomagnetic field models very well, but with a constant offset of 730 ± 90 yr. Possible reservoir effects from terrestrial pre-aging and hardwater effects can be excluded as the cause of the ∼730-yr offset because the different dated compounds correspond very well to each other, and modern reservoir effects are negligible. Instead, the constant ∼730-yr offset in the PSV pattern is likely the result of a constant lock-in depth of 26 ± 2 cm below the sediment-water interface at Khar Nuur. This assumption is supported by comparison of paleoclimatological proxies from Shireet Naiman Nuur, where similarities are obvious for the 14C-based chronology of Khar Nuur without a ∼730-yr adjustment. Therefore, the previously published 14C-based chronology of Khar Nuur provides a reliable age control. Accepting the lock-in depth of 26 ± 2 cm, the good consistency in inclination between Khar Nuur and global geomagnetic field models highlights the reliability of the latter even in a paleomagnetically understudied area.

The lack of systematic chronologies is a key problem for the archaeological sites of Altai and adjacent territories during the Great Migration Period. Here we present an attempt to establish the chronology of the Bulan-Koby culture objects of the Karban-I necropolis by correlation of accelerator mass spectrometry radiocarbon (AMS 14C) data from human remains with data from archaeological dating methods. This is the first application of such a combined targeted 14C and archaeological approach to the chronology of the Great Migration Period materials of northern Altai, and in particular the Bulan-Koby culture. Systematic analysis of the mutual occurrence of dated types of certain grave goods and 14C dating of a series of samples supports a predominant period of use for the site that spans the 2nd–3rd c. AD, which corresponds to the early Xianbei period. This study demonstrates strong agreement between the indicators obtained by archaeological and radiocarbon methods, suggesting chronological consistency of the necropolis which functioned at the beginning of the Great Migration Period. The very combination of the two techniques will allow more precise and detailed chronologies for other archaeological complexes of Altai and adjacent territories from the first centuries of the 1st mil. AD, which is the basis of historical reconstructions.

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.

In 2001, five French public organizations (CNRS, CEA, IRD, IRSN, and the Ministère de la Culture) signed an agreement to purchase a new accelerator mass spectrometer to provide radiocarbon dating services at the national level. The Laboratoire de Mesure du Carbone 14 (LMC14) was set up in Saclay (France) around ARTEMIS, an AMS system based on a 3MV Pelletron from NEC and installed in early 2003. In 2015, the LMC14 joined the Laboratoire des Sciences du Climat et de l’Environnement, making it possible to develop research projects in addition to the service activity and since 2021, the LMC14 has been a member of the IAEA Collaborating Centre “Atoms for Heritage” at the Université Paris-Saclay. Since 2003, 70,000 samples have been measured. Two-thirds of the samples have been prepared on site and one-third in two associated laboratories in Paris and Lyon. Over the past years, the LMC14 has participated in several international inter-comparisons and has continuously improved its capabilities by developing new protocols for preparation and measurement. In this paper, the radiocarbon dating services of the last 20 years for research institutions, museums and environmental monitoring are reviewed and recent results from environmental and archaeological research programs are highlighted.

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.