The direct dating of rock paintings is not always possible due to the lack of organic carbon compounds in pigments, or because sampling from a heritage site is often restricted. To overcome these limitations, dating laboratories have to develop new approaches. In this study, we consider sampling calcium oxalate crusts covering the painted artworks as a way to indirectly date the rock art. This stratigraphic approach includes isolating and extracting pure oxalate from the crusts. The approach was tested on natural bulk accretions collected in the open-air sites of Erongo Mountains in Namibia. The accretions were separated into two phases (pure oxalate and the remaining residues) with a special pretreatment. This process removes carbonates through acidification (HCl 6N) and dissolves the oxalate into the supernatant, leaving the minerals and windblown organic compounds in the residue. The efficiency of the separation was checked on the two phases by FTIR analyses and by 14C dating and showed that pure oxalate powders were indeed obtained. AMS radiocarbon results of various accretions on the same art panels provided ages from modern periods to 2410 ± 35 BP. From these first results, more targeted sampling campaigns can be considered to provide a terminus ante quem for the rock art.

Radiocarbon (14C) can be used to build absolute chronologies and reconstruct ocean ventilation over the last 40 ka. Sample size requirements have restricted 14C measurements in marine cores with low foraminifer content, impeding 14C-based studies focused on abrupt climate events. Recent developments have demonstrated that small-sized foraminifer samples can now be dated using a gas introduction system at the cost of a small decrease in precision. We explore the potential of gas measurements on benthic and planktonic foraminifers from core SU90-08 (43°03′1″N, 30°02′5″W, 3080 m). Gas measurements are accurate, reproducible within 2σ uncertainty and comparable to graphite measurements. Both techniques yield negative 14C benthic-planktonic (B-P) age-offsets after Heinrich event 1. We argue that negative B-P ages result from bioturbation and changes in foraminifer abundances, with the chance of negative B-P especially increased when the 14C age gradient between the deep and surface waters is decreased. Small-sized 14C measurements seem to capture the variance of the foraminifera age distribution, revealing the active mixing in those archives. Sediment deposition and mixing effects possibly pose a greater obstacle for past 14C-based dating and ocean ventilation reconstructions than the measurement precision itself, particularly in relatively low sedimentation rate settings.

Long-standing archaeological narratives suggest that the 3rd millennium cal BC is a key period in Mediterranean and European prehistory, characterized by the development of extensive interaction networks. In the Balkans for instance, the identification of such interactions relies solely upon typological arguments associated with conflicting local terminologies. Through a combination of 25 new radiocarbon (14C) dates and re-examination of the existing documentation, this paper defines the absolute chronology for groups which were previously only broadly framed into the 3rd millennium BC central Balkans (modern-day Serbia and North Macedonia). These absolute dates allow us to establish with greater clarity the chronological relations between different cultural groups that represent the main cultural units of the central Balkans sequence for the 3rd millennium cal BC: Coţofeni-Kostolac, Bubanj-Hum II, Belotić-Bela Crkva, Armenochori, and Bubanj Hum III. When comparing together the chronologies for material culture, funerary treatment of the body, and funerary architecture, there are no easily discernible patterns. We observe instead a complex mix of traits criss-crossing over a wide area encompassing the Pannonian basin, the central Balkans and the Greek peninsula.

A major threat to the Scotch whisky industry is the sale of counterfeit single malt whiskies with purported distillation years in the 19th and early- to mid-20th centuries. However, these are often much more recent spirits, distilled in the latter part of the 20th or first part of the 21st centuries. These sales impinge upon the reputation of auction houses, retailers, brand owners and distillers. The atmospheric testing of nuclear weapons in the 1950s and early 1960s has enabled a precise calibration curve to be created, however, there are several reasons why this may not be appropriate for establishing the year of whisky distillation. We have created a 14C calibration curve derived from known-age, single malt whiskies for the period 1950–2015 that enables whisky distilled during the period from 1955 onwards to have the distillation year determined to within 1–3 years for certain periods. However, because of the shape of the curve, two possible age ranges are often possible. The correct range can often be determined from a further plot of δ13C values against distillation year, which shows a trend of decreasing values through time. Several examples are given of the determination of both genuine and fake products.

The results of a short program of landscape, buildings and materials analysis undertaken at Achanduin Castle, Lismore, Scotland (NM 8043 3927) are presented from the pilot phase of the Scottish Medieval Castles & Chapels C14 Project (SMCCCP). The study presents the first independent chronological evidence relating to the construction of this important medieval building, by radiocarbon analysis of a limited assemblage of Mortar-Entrapped Relict Limekiln Fuel (MERLF) fragments. Informed by a wider investigation of structural phasing and sample taphonomy, these measurements are constrained within a series of different Bayesian models, to generate a range of comparative estimates for the building’s constructional chronology. The precision with which the construction of this building can now be dated, from other evidence associated with the site, makes the Achanduin Castle study a useful point of reference for wider materials research.

When sampling mortars for radiocarbon (14C) dating it is crucial to ensure that the sample has hardened rapidly relative the resolution of the dating method. Soft and porous lime mortars usually fulfill this criterion if the samples are taken from an uncovered surface from less than a few centimeters deep. However, hard, concrete-like mortars may be impermeable for carbon dioxide and even the outermost centimeters may still contain uncarbonated calcium hydroxide. These mortars may harden very slowly and contain carbonate that formed centuries or even millennia after the original building phase, and they can still be alkaline and capture modern 14C, causing younger 14C ages than the actual construction age. Another problem is reactivation of the binder carbonate if it has been partly decarbonated during a fire later on in its history. It will be shown that these young carbonates dissolve rapidly in phosphoric acid and in many cases a reasonable 14C age can be read from 14C profiles in sequential dissolution if the measurements from initially formed carbon dioxide are disregarded. However, if a mortar was made waterproof deliberately by adding crushed or ground tile, as in Roman cocciopesto mortars, it may be very difficult to get a conclusive dating.

To create a reliable radiocarbon calibration curve, one needs not only high-quality data but also a robust statistical methodology. The unique aspects of much of the calibration data provide considerable modeling challenges and require a made-to-measure approach to curve construction that accurately represents and adapts to these individualities, bringing the data together into a single curve. For IntCal20, the statistical methodology has undergone a complete redesign, from the random walk used in IntCal04, IntCal09 and IntCal13, to an approach based upon Bayesian splines with errors-in-variables. The new spline approach is still fitted using Markov Chain Monte Carlo (MCMC) but offers considerable advantages over the previous random walk, including faster and more reliable curve construction together with greatly increased flexibility and detail in modeling choices. This paper describes the new methodology together with the tailored modifications required to integrate the various datasets. For an end-user, the key changes include the recognition and estimation of potential over-dispersion in 14C determinations, and its consequences on calibration which we address through the provision of predictive intervals on the curve; improvements to the modeling of rapid 14C excursions and reservoir ages/dead carbon fractions; and modifications made to, hopefully, ensure better mixing of the MCMC which consequently increase confidence in the estimated curve.

Identifying and tackling recrystallization is a critical factor in the reliable radiocarbon (14C) dating of carbonates, since exogenous carbon can be incorporated and thus mask the real age of the samples. Vermetids are among the most important bioindicators used for paleo sea-level reconstruction, and the accuracy of their chronology can significantly impact sea-level curves. Age differences larger than 1 14C kyr before and after acid etching, combined with X-ray diffraction (XRD) analysis that indicates a significant amount of calcite still remains in the shell, led us to apply the previously developed carbonate density separation protocol (CarDS). Using a solution of sodium polytungstate, with density of 2.80 g/cm3, we successfully separated different carbonate fractions for a set of 10 vermetid samples from the coast of Rio de Janeiro, southeast of Brazil. Each separation was verified by XRD analysis and the 14C concentrations of different fractions were compared. The results show that the calcite fraction in the studied vermetid samples varied from 12 to 63% and aragonite fraction ages are up to 2 14C kyr older than the raw samples, thus confirming the efficacy of CarDS in removing young carbonates and the importance of density separation to vermetids prior to accelerator mass spectrometry (AMS) dating.

In order to assess late prehistoric human responses to climate change in the Western Loess Plateau (WLP), we investigated 13,567 charred plant seeds and 19 radiocarbon (14C) dates obtained from 41 late prehistoric sites in the upper Wei River valley. Based on these new dating results as well as their cultural attributes, these sites could be confidently divided into four chronological phases (Phase 1: Late Yangshao and Majiayao culture; Phase 2: Qijia culture; Phases 3 and 4: Siwa culture) but a significant gap was identified at ca. 3600–3000 cal yr BP in this region. Comparison of this interval to high-resolution paleoclimate records from Tianchi Lake suggests it could be attributed to the dramatic drop in temperature at this time. Accordingly, archaeobotanical evidence with a refined chronology shows the adoption of cold-tolerant subsistence cereal grains such as barley on the NETP (Northeast Tibetan Plateau). Drawing from various lines of knowledge (chronology, palaeoclimate, archaeobotany, and archaeology), it is reasonable to conclude that, even when confronting a similar magnitude of climate change, local human societies could vary tremendously. Different subsistence strategies were brought in by the trans-Eurasia culture exchange of prehistoric times.

The Centre for Isotope Research (CIO) at the University of Groningen has operated a radiocarbon (14C) dating laboratory for almost 70 years. In 2017, the CIO received a major upgrade, which involved the relocation of the laboratory to new purpose-built premises, and the installation of a MICADAS accelerator mass spectrometer. This period of transition provides an opportunity to update the laboratory’s routine procedures. This article addresses all of the processes and quality checks the CIO has in place for registering, tracking and pretreating samples for radiocarbon dating. Complementary updates relating to radioisotope measurement and uncertainty propagation will be provided in other forthcoming publications. Here, the intention is to relay all the practical information regarding the chemical preparation of samples, and to provide a concise explanation as to why each step is deemed necessary.

In this study, low temperature (room temperature, 400°C LT) and high temperature (400–900°C HT) of bulk organic carbon samples were dated from two loess and paleosol profiles. The results showed that radiocarbon (14C) dates of the LT were younger than HT fractions, indicating effect of younger contamination from overlying layers. The δ13C variation of the HT fraction appears to respond much more sensitively to climate change, and 14C ages of HT fraction can produce reasonable 14C ages from a younger layer, but it is very difficult to obtain reliable 14C ages from older layer as a result of uncomplete removal of young carbon.

Carbonaceous mortars from Novae (Bulgaria) contain local loess, crushed bricks and ceramic dust (pozzolanic materials). The reaction between lime and pozzolanic additives occurs easily and affects the rate and course of leaching reaction of carbonates in orthophosphoric acid during the sample pretreatment for dating. The composition of the Bulgarian mortars does not allow for unambiguous conclusions about chronology, but together with the observations of experimental mortars, gives new guidelines in terms of pozzolanic mortar application for dating. The presented research illustrates the possible reasons of difficulties with obtaining the appropriate portion of gas for radiocarbon (14C) measurement. To verify the relative chronology of legionary baths complex in Novae, the charcoals samples were also dated in addition to the mortar.

Beyond ~13.9 cal kBP, the IntCal20 radiocarbon (14C) calibration curve is based upon combining data across a range of different archives including corals and planktic foraminifera. In order to reliably incorporate such marine data into an atmospheric curve, we need to resolve these records into their constituent atmospheric signal and marine reservoir age. We present results of marine reservoir age simulations enabling this resolution, applying the LSG ocean general circulation model forced with various climatic background conditions and with atmospheric radiocarbon changes according to the Hulu Cave speleothem record. Simulating the spatiotemporal evolution of reservoir ages between 54,000 and 10,700 cal BP, we find reservoir ages between 500 and 1400 yr in the low- and mid-latitudes, but also more than 3000 yr in the polar seas. Our results are broadly in agreement with available marine radiocarbon reconstructions, with the caveat that continental margins, marginal seas, or tropical lagoons are not properly resolved in our coarse-resolution model.

Population density is an important variable in the development of social complexity. Estimating population densities from the archaeological record requires combining estimates of population, area, and time. Archaeological population estimates tend to be reported as a maximum population derived from the total accumulation of discrete archaeological material types, usually ceramics or radiocarbon (14C) dates. However, given the palimpsest nature of the archaeological record at recurrently occupied archaeological sites, these maximal, total estimates are, at best, a poor reflection of contemporaneous populations. I present a method for calculating average yearly population densities for occupations at a large, multicomponent site using a combination of distributional data and 60 14C dates. By employing this method at other sites in the same region, modeling intra-regional population dynamics at fine time scales will be possible.

Acid-alkali-acid (AAA) pretreatment is widely used to clean terrestrial plant macrofossil samples for radiocarbon (14C) dating. There is wide variation amongst laboratories in the AAA method details and less rigorous AAA pretreatment is often used on fragile or small samples. Yet there is little evidence as to the efficacy of the different methods and whether the use of less rigorous methods is justified. We investigated four variations of AAA pretreatment: acid only (no alkali wash); room temperature AAA; “standard” AAA at 85°C; and “aggressive” AAA at 85°C with alkali washes repeated until no discoloration was detected. We tested six different terrestrial macrofossils from four different locations and ranging in age from mid-Holocene to the Last Glacial Maximum. Our results demonstrate that while acid only is not always sufficient to remove young material, there is no difference in 14C age of samples pretreated by any of the AAA variants. We also observed mass loss of 85–90% in the standard and aggressive AAA pretreatments, and much more modest mass loss in the room temperature AAA pretreatment. Therefore, we conclude that room temperature AAA pretreatment is optimal to remove contaminating material from fragile terrestrial macrofossils while retaining the majority of the authentic sample material.

New radiocarbon (14C) dates suggest a simultaneous appearance of two technologically and geographically distinct axe production practices in Neolithic Britain; igneous open-air quarries in Great Langdale, Cumbria, and from flint mines in southern England at ~4000–3700 cal BC. In light of the recent evidence that farming was introduced at this time by large-scale immigration from northwest Europe, and that expansion within Britain was extremely rapid, we argue that this synchronicity supports this speed of colonization and reflects a knowledge of complex extraction processes and associated exchange networks already possessed by the immigrant groups; long-range connections developed as colonization rapidly expanded. Although we can model the start of these new extraction activities, it remains difficult to estimate how long significant production activity lasted at these key sites given the nature of the record from which samples could be obtained.

Marine mollusk shells have been extensively used to provide radiocarbon (14C)-based chronologies in paleoenvironmental and archaeological studies, however uncertainties in age measurements are introduced because secondary factors such as vital effects and diet may influence 14C incorporation into these shells. Deep burrowing and deposit feeding mollusks, in particular, may incorporate “old” carbon resulting in apparently older ages than their contemporary environment. In this study, we present paired 14C and stable isotope (δ13C and δ18O) measurements for nine species of known-age bivalves having different feeding strategies and collected in six localities around the NE Atlantic. We exclude potential “old” carbon contamination in these known-age mollusk shells, acquire a better understanding of local ecology and provide an improved context for the environmental interpretation of 14C ages. Our results indicate that, in the NE Atlantic, marine mollusk-derived 14C ages provide a reliable basis for environmental and archaeological investigation, independently of vital effects and differences in microhabitats, feeding strategies and sample location—all of which are apparent from stable isotopes.

The ages of mortars and plaster can help reveal the history of monuments, their construction, or restoration times. However, these anthropogenic carbonates pose a challenge when it comes to separation of the atmospheric radiocarbon (14C) signal of the CO2 fixed in the mortar at the time of consolidation, i.e., the time of binder formation. The variety and heterogeneity of mortars require individual assessments of each sample and 14C results. Here we present our current preparation method and summarize experience based on results collected during the last 20 years of mortar dating at the ETH laboratory.

A zolnik excavated in 2016–2018 at the hillfort identified as the Scythian cultural circle in Chotyniec (southeastern Poland, 8 km west of the current Poland–Ukraine border) provided a very large quantity of archaeological sources and organic materials. From the latter, 17 samples coming from different horizons were selected for dating and were used to build a chronological model of functioning of the zolnik. Absolute dating is particularly important because the discovered artifacts (especially the most common handmade ceramics) do not show large chronological diversity. The use of the zolnik was estimated at 250–300 years, i.e. between 7th/6th and 4th/3rd century BC. Stratigraphic observations and good references of absolute chronology based on artifacts, including imported Greek ceramics, first in this part of Central Europe, proved to be significant. Older radiocarbon dates correspond to typological dating of Greek amphoras (7th/6th–6th century BC).

Fewer than 200 radiocarbon (14C) dates with secure contextual information are available for Cuba, making it challenging to reconstruct Caribbean indigenous population dynamics, their identities and interactions. In this paper, we discussed 21 accelerator mass spectrometry (AMS) 14C dates from two mounds (M1 and M2) at the Playa del Mango site (Granma province, Cuba), traditionally associated with the Banwaroid stone tool tradition. The ΔR calculated for the site was –132.0 ± 176 and –164.0 ± 68. The chronology of burials from the peripheral area of M2 suggested that the cemetery was continuously used from at least cal BC 116–AD 241 (2 σ). The domestic area of M2 was used at minimum between cal BC 55–AD 435 (2 σ), which encompasses the use of the funerary areas. An isolated human tooth from M1 [cal AD 125–435 (2 σ)] suggested that this funerary area is later than the one at the periphery of M2, and possibly contemporaneous with the later formation of the M2 shell midden. The archaeological assemblage of the “Banwaroid tradition” is widely distributed in Cuba, and mixed with other archaeological traditions, supporting that a complex web of human interactions took place in the Caribbean in precolonial times.