The analysis of processing standards alongside samples for quality assurance in radiocarbon (14C) analyses is critical. Ideally, these standards should be similar both in nature and age to unknown samples. A new compound-specific approach was developed at the University of Bristol for dating pottery vessels using palmitic and stearic fatty acids extracted from within the clay matrix and isolated by preparative capillary gas chromatography. Obtaining suitable potsherds for use as processing standards in such analyses is not feasible, so we suggest that bog butter represents an ideal material for such purposes. We sampled ca. 450 g from two bog butter specimens and homogenized them by melting. We verified the homogeneity of both specimens by characterization of their lipid composition, δ13C values of individual lipids, and both bulk- and compound-specific radiocarbon analyses on 10 sub-samples of each bog butter specimen. The weighted means of all 14C measurements on the bog butter standards are 3777 ± 4 BP (IB33) and 338 ± 3 BP (IB38), thereby providing age-relevant standards for archaeological and historical fatty acids and ensuring the accuracy of radiocarbon determinations of lipids using a compound-specific approach. These new secondary standards will be subjected to an intercomparison exercise to provide robust consensus values.

Tsunamis are huge disasters that can significantly damage benthic organisms and the sea-bottom environment in coastal areas. It is of great ecological importance to understand how benthic ecosystems respond to such destructive forces and how individual species are affected. Investigating the effect of such disasters on animals that are seldom caught alive is particularly difficult. Bivalve mollusks are especially suitable for investigating how a tsunami affects coastal benthic species because they preserve an environmental record in their shells that can be extended back in time by crossdating the records of multiple individuals. Here we studied dead shells of Mercenaria stimpsoni, a long-lived clam, and precisely determined the time of death by using nuclear bomb–induced radiocarbon (bomb-14C) and by counting annual growth increments. First, a quasi-continuous, regional bomb-14C record was created by analyzing the shells of 6 live-caught M. stimpsoni individuals. Then 27 dead shells collected from the seafloor of Funakoshi Bay were 14C-dated and analyzed. The results showed that the huge tsunami that struck northeastern Japan on 11 March 2011 caused mass mortality of this bivalve in Funakoshi Bay. Nine of the 27 clams died during the March 2011 tsunami, probably by starvation after burial by tsunami deposits or exposure above the seafloor as a result of sediment liquefaction during the earthquake. The dating method used in this study can help us understand how long-lived marine organisms with low population density are affected by huge natural disasters such as a tsunami.

The paper presents and discusses a series of radiocarbon (14C) dates from a medieval Nubian monastery found on Kom H of Old Dongola, the capital of the kingdom of Makuria located in modern-day Sudan. The monastery was founded in the 6th–7th century AD and although it probably ceased to function in the 14th century, the site remained occupied until the beginning of the 15th century. The investigated courtyard of the monastery was in use from the 11th to the 14th century, as indicated by the ceramics and 14C analysis results presented here. The dates under consideration are the first published series of 14C dates from this site, which is of crucial importance for historical research on medieval Nubian Christianity and monasticism. They permit to begin building an absolute chronological framework for research on the archaeological finds from the site and region. A group of finds in particular need of such a framework are ceramics, and the implications of the 14C dates for pottery assemblages found in the dated contexts are discussed. The conclusions summarize the significance of the datings for the history of the site.

Collagen extraction depends on the state of bone preservation, and the acidity of Brazilian soils often prevents the use of this material for radiocarbon dating. When available, however, bone samples constitute very important chronological records for both archaeological sites and natural depositional sites of specific animals. The extraction of collagen was performed using two filters, the first aiming to remove insoluble contaminants, and the second, a vivaspin ultrafilter 30KD to retain large molecular weight materials. The collagen was liofilized and converted to CO2 by combustion in sealed quartz tubes with CuO and Ag. The graphite was produced by zinc reduction in independently sealed Pyrex™ tubes. In order to verify the accuracy of this protocol, we analyzed a modern bone and four previously dated fragments, including those from the Sixth International Radiocarbon Intercomparison (SIRI), and a fragment of human bone from the Amourins site, a Brazilian shellmound. The results for the known age material are in agreement with the expected and the studied sector of Amourins shellmound was dated 4100–3900 years cal BP from a chronological model performed with charcoal dating found in different stratigraphic layers. Samples were dated at the radiocarbon laboratory of Universidade Federal Fluminense (LAC-UFF) in Brazil.

Triliths are megalithic monuments scattered across the coastal plains of southern and southeastern Arabia. They consist of aligned standing stones with a parallel row of large hearths and form a space, the meaning of which is undoubtedly significant but nonetheless still unknown. This paper presents a new radiocarbon (14C) dataset acquired during the two field seasons 2018–2019 of the TSMO (Trilith Stone Monuments of Oman) project which investigated the spatial and temporal patterns of the triliths. The excavation and sampling of trilith hearths across Oman yielded a dataset of 30 new 14C dates, extending the use of trilith monuments to as early as the Iron Age III period (600–300 BC). The earlier dates are linked to two-phase trilith sites in south-central Oman. The three 14C pairs collected from the two-phase trilith sites indicated gaps between the trilith construction phases from 35 to 475 years (2 σ). The preliminary spatio-temporal analysis shows the geographical expansion of populations using trilith monuments during the 5th to 1st century BC and a later pull back in the 1st and 2nd century AD. The new 14C dataset for trilith sites will help towards a better understanding of Iron Age communities in southeastern Arabia.

The Suyanggae archeological complex is located in Aegok-li, Danyang County, Chungbuk Province, Korea (128°20'00"E, 365˚7'15"N, elevation 132 m). We investigated two Suyanggae Paleolithic localities (1 and 6). A total of 31 samples (18 localities) were analyzed for radiocarbon (14C) ages in three paleolithic cultural horizons of Suyanggae Locality 6 (SYG-6). The purpose of this paper is to report all dating results of SYG-6. It was found that ranges of 14C ages (BP) of cultural layers of SYG-6 are known to be 17,550 ± 80 ∼ 20,470 ± 70, 30,360 ± 350 ∼ 44,100 ± 1900, and 34,870 ± 540 ∼ 46,360 ± 510 BP for cultural layers 2, 3, and 4, respectively. We compared these age data with those of the previous study associated with Gunang Cave near Suyanggae Locality 1 (SYG-1). Based on the chronological information of the three archaeological sites, early humans lived in a rather cold environment from approximately 30,000 to 46,000 BP and disappeared between 30,000 ∼ 20,000 BP and then settled again in SYG-6 site during LGM period. This study demonstrates that archaeological study is important not only for understanding human occupations with their cultural development but also establishing climatic signals to which they have been adapted as a part of the human evolutional process.

We present a new biennial record of radiocarbon (14C) measured in Danish oak. The new record covers the years 1251–1378 CE, thereby spanning the Grand Solar Minimum known as the Wolf Minimum. Two oak samples from every other year were measured at the AMS facility at Aarhus University (Denmark), resulting in an average precision of 1.4‰ for the record. Spectral analysis of the new record revealed two peaks at 27 and 9.1 years, which could indicate the Hale cycle was lengthened and the Schwabe cycle shortened during the Wolf Minimum, but it is also possible that the amplitude of the Schwabe cycle was too small to be accurately identified with the acquired precision of this record. The record was bandpass filtered to investigate the variability of the amplitude in different bands, which showed a dampening of the amplitude during the second half of the Wolf Minimum in bands centered on the Schwabe and the Hale cycle, respectively. A reconstruction of the solar modulation function, Φ, also showed a periodicity of ca. 9 years, and indicated that the Wolf Minimum was preceeded by one cycle of decreased solar activity.

This study is on the absolute age dating of a multicultural site of Erenda, East Medinipur district, in coastal West Bengal, India. Charcoal samples were collected and measured using the accelerator mass spectrometry (AMS) facility at the Inter-University Accelerator Centre, New Delhi, India. These samples were collected from secured stratigraphic context of two excavated trenches. A careful collection of samples from two trenches provided us with the first calendar dates, 950 BCE and 1979 BCE, of protohistoric sites in coastal West Bengal. These calibrated calendar dates not only have wider significance in terms of archaeology but also methodological implications to understand the relevance of application of AMS from the dynamic coastal landscape in the humid tropics during the late Holocene period.

The complex geographical scenario of Mexico allowed the cultural diversification and development of multiple cultures such as Tolteca, Teotihuacan, Mexica, and Maya, among others. Despite this rich cultural heritage, radiometric dating of Mexican cultural samples with radiocarbon (14C) began only in the 1980s and with accelerator mass spectrometry (AMS) in 2013. Analysis of 14C with AMS is the most widely used technique to date archaeological objects and cultural heritage. Since 2013, the Accelerator Mass Spectrometry Laboratory (LEMA) facility of the Institute of Physics at UNAM (IF-UNAM) has supported archaeological research in Mexico, but also investigation in other areas such as geology, physics, chemistry, and environmental sciences through the analysis of 14C, 10Be, 26Al, 129I, and Pu. The absolute dating with 14C continues to be the core of LEMA’s work, where different geographical scenarios of the country and climatic conditions present very diverse analytical challenges. This work presents a basic description of the AMS system of the LEMA laboratory and describes some applications that are currently being developed.

The Kostenki-Borshchevo site complex (Voronezh region, Russia) serves as the foundation of Eastern Europe’s Upper Paleolithic chronocultural framework. Here we present new radiocarbon dates for three Kostenki sites. Dates of ∼27.5–27 ka BP for Kostenki 15 suggest that its archaeological layer accumulated over a short period. These results help to confirm that the site is unrelated to Aurignacian assemblages. New dates for the Kostenki-Avdeevo Culture (KAC) Layer I of Kostenki 1 address the longstanding question of its chronology. Our results of ∼23.5–23 ka BP from different areas of the site are consistent with the layer’s accumulation over a short period. These results accord with recently obtained dates for Kostenki’s other KAC sites. Our younger results of ∼22.5–21 ka BP for different material from Layer III of Kostenki 21 are similarly consistent with a short chronological window for Kostenki’s KAC sites. Overall, this and other recent publications support the view that many Kostenki assemblages are chronologically distinct. This provides an important insight into the tempo of Upper Paleolithic cultural change.

A laboratory intercomparison project was carried out on 20 annually resolved late-wood samples from the Danish oak record. The project included the following three laboratories: (1) the University of Arizona AMS Laboratory, University of Arizona, USA (AA); (2) HEKAL AMS Laboratory, MTA Atomki, Hungary (DeA); and (3) Aarhus AMS Centre (AARAMS), Aarhus University, Denmark (AAR). The large majority of individual data points (96%) lie within ±2σ of the weighted mean. Further assessment of the accuracy associated with the individual laboratories showed good agreement, indicating that consistent and reliable 14C measurements well in agreement with each other are produced at the three laboratories. However, the quoted analytical uncertainties appear to be underestimated when compared to the observed variance of differences from the geometric mean of the samples. This study provides a general quality check of the single-year tree-ring 14C measurements that are included in the new calibration curve.

The article reports on a new sampling method and the archaeological context of cave drawings, which include the oldest currently known graffiti in the Czech Republic. Between 2016 and 2020, samples with a small amount of charcoal were taken from drawings found in Kateřinská Cave (Catherine’s Cave) of the Moravian Karst in the Czech Republic. A new gentle method of sampling charcoal from the cave walls was developed for the purpose of radiocarbon (14C) dating cave drawings of unknown age, while preserving the contours of the drawings. 14C analysis has provided data from four periods of prehistory and history: from the Neolithic around 5000 BC, the turn of the Neolithic and Eneolithic around 4300 BC, the Hallstatt Period from 800–450 BC, and also from the Middle Ages (13th century). The radiocarbon dates of the graffiti correspond to the dates of the pottery finds from the entrance portal of Kateřinská Cave, thus validating the dates and the sampling method.

The Mexico City Basin has had exceptional plant and animal diversity since ancient times due to its varied orography and benign climate. This environment attracted diverse human groups, from hunter-gatherers to one of the most influential pre-Hispanic cultures of Mesoamerica: the Mexica, also known as the Aztec. The subsoil of Mexico City hides a rich and varied cultural heritage. The Archaeological Rescue Department works to preserve cultural heritage, review archaeological studies, and expand archaeological information with new findings. We report on archaeological rescue works carried out at two sites in the Mexico City Basin prior to the beginning of new construction projects. The first one is the Reforma Hidalgo Complex Office in Teocaltitlán, one of the neighborhoods of ancient Mexica City, Mexico-Tenochtitlan. Some wooden post samples were selected for accelerator mass spectrometry radiocarbon (AMS 14C) dating, believed to have been used as chinampa supports. We seek to determine their temporality and possible reuse by Hispanic builders. The second one, the La Otra Banda Site, is part of the human settlements that were founded around Cuicuilco, one of the main ancient urban centers of the highlands of Central Mexico. Some human bones and coal samples were selected to be dated, aiming to establish the site’s occupation time.

Since radiocarbon accelerator mass spectrometry (14C AMS) is considered a high-precision technique, reassessment of the measurement uncertainty has been a topic of interest. Scientists from analytical and metrological fields have developed the top-down and bottom-up measurement of uncertainty approaches. The 14C quoted error should approximate the uncertainty of long-term repetitions of the top-down approach in order to be realistic. The novelty of this paper is that the uncertainty of both approaches were approximated to each other. Furthermore, we apportioned the graphitization, instrumentation, and bias components in order to additively expand the quoted error. Our results are comparable to error multipliers and to long-term repeatability studies reported by other laboratories. Our laboratory was established in late 2012 with N2 as stripper gas and 7 years later, we changed to helium stripper. Thus, we were able to compare both gases, and demonstrate that helium is a better stripper gas. In absolute F14C units, the ranges of graphitization+bias combined uncertainties were (0.7 to 4.1) × 10–3 for N2 and (0.7–3.0) × 10–3 for He depending on the standard 14C content. The error multiplier for He defined as the expanded uncertainty over quoted error, in average, was 1.7; while without the bias, the multiplier was 1.3.

Medieval manuscripts are invaluable archives of the written history of our past. Manuscripts can be dated and localized paleographically, but this method has its limitations. The Fragmenta membranea manuscript collection at the National Library of Finland has proved difficult to date using paleographic methods. Radiocarbon dating has been applied to manuscripts of parchment before, but a systematic protocol for radiocarbon dating of parchment has not been established with a minimally destructive sampling strategy. In this work, we have established a radiocarbon dating procedure for parchments combining a clean-room based chemical pretreatment process, elemental analyzer combustion, automatic graphitization and accelerator mass spectrometry (AMS) measurements to reduce the AMS target size from a typical 1 mg of carbon. Prolonged acid treatment resulted in improved dating accuracy, since this is consistent with the manufacturing process of medieval parchment involving a lime bath. Two different combustion processes were compared. The traditional closed tube combustion (CTC) method provided a well-established though labor-intensive way to produce 1 mg AMS targets. The Elemental Analyzer-based process (EA-HASE, Elemental Analyzer Helsinki Adaptive Sample prEparation line), is designed for fast combustion and smaller sample sizes. The EA-HASE process was capable of reproducing the simulated radiocarbon ages of known-age samples with AMS graphite target sizes of 0.3 mg of carbon, corresponding to a 3 mm2 area of a typical medieval parchment. The full potential of the process to go down to as little as 50 μg will be further explored in the future in parallel to studies of sample-specific contamination issues.

The Nekselø Wickerwork provides an unusually solid estimate on the marine reservoir age in the Holocene. The basis for this result is a 5200-year-old fish weir, built of hazel wood with a brief biological age of its own. Oysters settled on this construction. They had lived only for a short number of years when the fence capsized and was covered in mud and the mollusks suffocated. Based on the difference in radiocarbon (14C) age between accelerator mass spectrometry (AMS) samples of oyster shells and wood, respectively, the marine reservoir age for this site is estimated to 273 ± 18 14C years. Re-evaluations of previously produced data from geological and archaeological sites of Holocene date in the Danish archipelago indicate marine reservoir ages in the same order as that of the Wickerwork. Consequently, we recommend the use of the new value, rather than the ca. 400 14C years hitherto favored, when correcting for the dietary induced reservoir effect in radiocarbon dates of humans and animals from the Late Mesolithic and Early Neolithic periods of this region.

According to the classical chronology of the Inca State, the ascension to power of Pachacuti Inca took place around AD 1438 and the construction of Machu Picchu began by AD 1450–1460. However, the improvement in the accuracy of radiocarbon (14C) dating resulting from the application of Bayesian analysis has changed our view of the historical chronology. This new research raises questions about our understanding of the cultural development of the Machu Picchu area, in the light of the new proposed chronological scheme. This paper presents a set of 11 new 14C dates, derived from AMS, from the sites of Llaqta of Machu Picchu, Chachabamba, and Choqesuysuy. The latter two sites are situated within the Machu Picchu National Archaeological Park (Arqueología del Santuario Histórico Nacional y Sitio Patrimonio Mundial de Machu Picchu) and have been interpreted as being part of the contemporary Late Horizon Inca landscape. The new 14C ages are modeled using Bayesian inference and present a revised dating framework for these sites and their chronological relationship with Llaqta of Machu Picchu.

A new series of 19 radiocarbon dates provides new insights on the human settlement activity in central Ukraine. The paper presents data from the Early Holocene until the establishment of Trypillian mega-sites in the late Vth mill. BC. Our new dates from a long sequence of the site of Melnychna Krucha refine the chronology of the Middle and Late Mesolithic and local ceramic-bearing “Buh-Dniester” culture. Additional dates were obtained on bones from Linear Pottery culture sites and Trypillian sites of stages A3 and B1.

This study obtained calendar dates by radiocarbon accelerator mass spectrometry (14C AMS) dating sequential tree-rings of wooden support posts from the buried remains of traditional Kitkahahki Pawnee earthlodges preserved at an archaeological site on the Central Great Plains, USA. The tree-ring segments from the site were dendrochronologically analyzed prior to this study, but the cross-matched site chronology could not be definitively cross-dated and was thus “floating” in time. Our study represents the first floating tree-ring chronology from the Great Plains to be anchored in time by means of independent radiocarbon analysis. Three specimens were analyzed and dated to 1724–1774 CE (82.0% probability), 1774–1794 CE (95.4% probability), and 1800–1820 CE (95.4% probability). These dates correspond to the hypothetical timing of Kitkahahki ethnogensis, the main phase of village growth in the area, and a later reoccupation during a turbulent period in regional history. The results of this study conform to a scenario in which chaotic social conditions correspond to an increase in residential mobility between the core of Pawnee territory and a southern frontier in the Republican River valley.

El Mirón is an important archaeological cave site in Cantabria (Spain) with a stratigraphy covering the late Middle Paleolithic to the Modern Period. The Magdalenian levels are especially rich in artifacts, faunal remains, and features, and included the burial of an adult female (“the Red Lady”), as well as other scattered human remains, while the Neolithic levels contained the oldest combined evidence of ceramics, domesticated grain and livestock in the region. However, in the absence of diagnostic artifacts in many levels that would always provide a traditional cultural chronology, radiocarbon dating has been essential in understanding the temporal framework for human activity at the site. Over the duration of more than two decades, the El Mirón Project has therefore obtained 93 radiocarbon dates, which cover the entire stratigraphic record as found in several different excavation areas. In light of the considerable methodological advances that radiocarbon dating has seen since 1996 we aim to evaluate the reliability of the published 14C record for El Mirón Cave, and to improve the accuracy of the radiocarbon based chronostratigraphy through Bayesian modeling. The results shed light on which dates may be used for future research and where dating discrepancies reflect taphonomic processes, thereby advancing intra-site and regional archaeological comparisons.