The sealed tube Zn reduction method has been applied for small-mass samples ranging from 15 to 100 μg carbon preparation for accelerator mass spectrometry (AMS) radiocarbon (14C) measurements at the AMS-14C Preparation Lab in Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS). The volume of the sealed reactor tube is reduced to ~0.75 cm3 in order to increase the yield of graphite. Graphite targets are measured at the Keck Carbon Cycle AMS Facility at the University of California, Irvine (KCCAMS). The targets generate a maximum 12C+1 current of about 0.5 μA per 1 μg C. The modern-carbon background is estimated to be 0.25–0.60 μg C, and dead-carbon background to be ~0.3–0.9 μg C. Both modern-carbon background and dead-carbon background are size dependent, so the results can be corrected. The precision of the small-mass modern carbon standard samples is±15–25‰ for the size of ~15–20 μg C,±5–10‰ for ~20–50 μg C, and±3–10‰ for 50–100 μg C. Further reduction of dead-carbon and modern-carbon contamination is needed in preparation of small-mass samples at GIGCAS.

Vitória Bay is located in the south-central part of the State of Espírito Santo (SES). Multiproxy analyses were performed on samples from a 490-cm-long sediment core collected at the coordinates 40°18′23′′W and 20°14′48′′S. The objective of this study was to identify and integrate the multiproxy data to determine the environmental dynamics during the Holocene. The material was subsampled every 10 m and submitted to standard methodological processing. The sediment core was dated to two depths: the oldest age was between 9396 and 9520 cal yr BP at a 480-cm depth, and the youngest age was from 7423 to 7511 cal yr BP at a 304-cm depth. The integrated analysis revealed evidence of three major environmental changes in Vitória Bay. The first phase had a fluvial influence (depth of 490–480 cm; 9396–9520 cal yr BP). This was followed by a transitional period (depth of 480–290 cm; 7423–7511 cal yr BP) with a salt influence due to the Last Marine Transgression (LMT). Later, the environmental stability was similar to that of today (290 cm to the core top). This was a reflection of the Last Marine Regression (LMR) in the Holocene.

The tuning of plateaus in glacial and deglacial planktic radiocarbon records to pertinent structures in the atmospheric 14C record of Lake Suigetsu results in both a record of surface water reservoir ages and a centennial-scale absolute age model. However, the atmospheric origin of planktic 14C plateaus may be questioned. Alternatively, plateaus may result from short pulses of increased hemipelagic sediment deposition, which challenges the technique of 14C plateau tuning. To test the two rationales for the interval 23–12 cal ka, we calculated hypothetical sedimentation rates for all 14C plateaus identified in five Atlantic sediment cores assuming sediment pulses that either span 10, 100, 200, or 300 yr each. These rates were compared to rates derived by 14C plateau tuning that assumes an atmospheric origin of the plateaus. In each plateau suite, our hypothetical sedimentation rates result in at least one or two cases in extreme values that exceed the rates reported for short-lasting pulses of sediment deposition in contourites by a factor of 50 and therefore appear unrealistic. Moreover, they result in entire suites of plateau structures that incidentally appear closely aligned to the pattern of atmospheric 14C plateau suites rather than to any pulses of climate-controlled sediment discharge.

Early Medieval stone building began earlier and was more widespread than previously thought. This conclusion is the result of scientific dating that challenges traditional views of the “petrification” process in architecture north of the Alps after the Roman period. Radiocarbon (14C) dating is not precise enough to answer detailed questions connected to historical contexts, but recently there have been a number of surprising dates: “Roman” city walls have now Early Medieval phases or meter-high, obscure “dark earth” strata were subdivided and dated. Results not in line with clients’ expectations can be the subject of heated debates, or worse, tend to remain unpublished. To the archaeologist, who is trying to connect scientific dates with historical events, usually is not clear, that mortar dating is a methodology still being developed, while dating organic material like charcoal from mortar is a standard procedure. But even the latter has downfalls like the possible “old-wood-effect,” if such complications are not carefully considered and avoided during the sampling process. Drawing on examples from Switzerland, Germany, Austria, and France, recent challenging results will be discussed from an archaeologist’s point of view.

A special type of coastal settlement, promontory forts defended by inland-facing walls, appeared in the Balearic Islands in an imprecise time during the Bronze Age. A research project was initiated in 2011 to study one of these sites on each of the two major islands of the archipelago. The first one, Es Coll de Cala Morell (north Menorca), is a walled promontory with a relatively large plateau, with 13 horseshoe-shaped houses (navetes). The second, Sa Ferradura (east Mallorca), is a smaller coastal cape, with a different spatial planning, with only two large built-up areas, both attached to the enclosure wall. Two of the navetes have been excavated at Es Coll de Cala Morell, showing a domestic space with a central hearth in both cases. The occupation has been dated to around 1600–1200 cal BC. At Sa Ferradura seven hearths have been recorded in a large, open-air area. Their chronology falls within the interval of approximately 1200/1100–900 cal BC. From a chronological point of view, fortified settlements in coastal promontories are not, as was expected, a unitary phenomenon in Menorca and Mallorca and have to be related to different cultural periods.

This article presents the results of interdisciplinary analysis of samples from the Czarnówko archaeological site in northern Poland, reporting the first radiocarbon dates for the site in comparison with its relative chronology. The site is of high importance because of its scale and opulence of artifacts. It was used for over 900 yr, from the 7th century BC up to the 3rd century AD, by populations of different cultures (the Lusatian, Pomeranian, Oksywie, and Wielbark). Samples of charcoal, wood, and textile were collected from different features, most of them from burials. Charcoal was taken from cremation pits, while wood was sampled from coffins in skeletal burials. Among samples collected during archaeological excavations in 2008 and 2010, 20 were chosen for 14C dating and macro- and microscopic observations. Images taken using a scanning electron microscope revealed the microstructure and preservation level of the specimens. An emphasis was also placed on geomorphological and geological research of the site area to gain information about the environmental conditions influencing the samples’ preservation state, e.g. pH, type, origin and permeability of sediment, and accumulation of organic matter. The obtained calibrated 14C ages are in agreement with the relative chronology based on the typology of artifacts and stratigraphic site reconstructions.

The authors have developed an active absorption system combining a molecular sieve with a pressure gradient as a way to overcome the shortcomings of the phosphoric acid solution displacement method. Taking advantage of the pressure gradient produced between the inside and outside of a bottle, as water moves through it, CO2 in the atmosphere can actively be absorbed onto a molecular sieve in its pathway. A comparative study showed that the technique was in agreement with the phosphoric acid displacement method, within error. We applied the new method to collect not only atmospheric CO2 samples, but also CO2 samples from soil respiration to verify its utility. Simple yet practical, our method is well suited to extended collection times in a variety of environments, and capable of providing relatively large amounts of carbon for high-precision accelerator mass spectrometry (AMS) 14C analyses of atmospheric samples.

The main objective of this report is to present the dating process routinely applied to different types of samples at the Laboratoire de Mesure du Carbone 14 (LMC14). All the results and protocols refer to our procedures over the last 5 years. A description of the sorting and chemical pretreatments of the samples as well as the extraction and graphitization of CO2 are reported. Our last study concerning the degradation of the blank level according to the storage time of the targets between graphitization and accelerator mass spectrometry (AMS) measurement is also presented. This article also provides information on how to submit a valid laboratory sample. We give details relating to sampling procedures on site as well as contamination issues relative to the 14C dating methodology.

The transition from the Middle to Late Pre-Pottery Neolithic B (PPNB) happened throughout southwest Asia in the mid-8th millennium cal BC. It entailed the abandonment of a number of sites, rapid growth of others, as well as the wide spread of morphologically domestic caprines. What remains an unknown is how rapid these processes were in real time. Over the period when the transition was taking place, the calibration curve has two shallow sections divided by a sudden drop, which for many of the older dates creates an illusion of a sudden cultural break around 7600–7500 cal BC. Yet a more detailed study presented in this paper suggests that the transition event could have been spread over a more extended period of time. This, however, is still far from certain due to risks of old wood effects and complexities of site formation.

Compound-specific radiocarbon analysis (CSRA) of benzene polycarboxylic acids (BPCAs) yields molecular-level, source-specific information necessary to constrain isotopic signatures of pyrogenic carbon. However, the purification of individual BPCAs requires a multistep procedure that typically results in only microgram quantities of the target analyte(s). Such small samples are highly susceptible to contamination by extraneous carbon, which needs to be minimized and carefully accounted for in order to yield accurate results. Here, we undertook comprehensive characterization and quantification of contamination associated with molecular radiocarbon (14C) BPCA analyses through systematic processing of multiple authentic standards with both fossil and modern 14C signatures at various concentrations. Using this approach, we precisely apportion the contribution of extraneous carbon with respect to the four implemented subprocedures. Assuming a constant source and quantity of extraneous carbon we correct and statistically evaluate uncertainties in resulting 14C data. Subsequently, we examine the results of triplicate analyses of reference materials representing four different environmental matrices (sediment, soil, aerosol, riverine natural organic matter) and apportion their BPCA sources in terms of carbon residues derived from biomass or fossil fuel combustion. This comprehensive approach to CSRA facilitates retrieval of robust 14C data, with application in environmental studies of the continuum of pyrogenic carbon.

This paper presents radiocarbon (14C) dating of Scythian period sites discovered in Northern Altai, Russia, in the 1990s, including large, unlooted barrow cemeteries in the Manzherok region. The results indicate that barrows attributed to the Karakoba culture may represent a long time span from the beginning of the 9th century BC until the beginning of 1st century BC, while those linked with the North Pazyryk culture generally keep within the Scythian period: from the beginning of the 5th century BC to the late 1st century AD. 14C analysis has confirmed the viability of traditional archaeological dating and the contemporaneity of barrows belonging to various cultural traditions (North Pazyryk, Karakoba), and also allowed correlating the horizons of burials to the seismic phenomena observed at the site.

From the early days of radiocarbon dating, the standard sample treatment has involved removal of contamination from carbonates and humic acids by washes in acid and base, respectively. A modification of this acid-base-acid (ABA) method has been suggested, especially for material older than 20,000 yr. However, the criticism of ABA and application of a more aggressive oxidizing method, such as wet oxidation (ABOX) or cellulose extraction, might only be needed in some special cases, for example, in the case of poorly preserved or chemically treated wood. Separation of cellulose seems to be the ultimate solution; however, it is not always applicable when samples contain small amounts of wood. As a part of studies focusing on the chronology of late Pleistocene sedimentary processes in the Venetian–Friulian Plain and Carnic Alps (NE Italy), 14C analyses were performed on old wood samples found in sedimentary deposits of pre-Last Glacial Maximum (LGM) age. Wood samples were treated by five methods: ABA, two modified ABA treatments (ABOX and ABA+Bleach), as well as two different cellulose separations. Infrared spectra of treated samples and 14C results show that in most cases the ABA method is sufficient in removing the contamination of naturally deposited wood, even when the wood is of very old age.

This article presents the results of direct accelerator mass spectrometry (AMS) radiocarbon dating of a new bone anvil retrieved in the Iron Age–Roman site of Montefí (Ciutadella), in the southwest of the island of Menorca (western Mediterranean). The radiometric date confirms the chronology obtained through the stratigraphy and typological analysis of ceramics (1st–3rd century AD), and indicates that this bone-made tool not only represents the first archaeological anvil from the island but also constitutes the earliest evidence in the western Mediterranean. This ancient date is more consistent with the known eastern regional chronology and reinforces the importance of obtaining direct AMS 14C dates to refine artifact chronologies.

This study investigates human environmental adaptation in northern Finland at the cemetery of Iin Hamina. The cemetery was in use in the 15th and 16th centuries AD during the cool climate anomaly called the Little Ice Age. It is possible that these extreme climatic conditions may have impacted human survival in this agriculturally marginal region. In previous studies, carbon and nitrogen isotopes in the bone collagen of humans and fauna have shown that the main protein source for people at Iin Hamina was fish. In this study, I observe annual changes in diet derived from isotopic studies of teeth. Apart from one individual whose protein source shifted radically during tooth formation, the results show the inhabitants of Iin Hamina experienced only minor changes in diet over periods of several years. Moreover, none of the dietary profiles provided evidence of dietary or physiological stress through raised nitrogen isotope ratios. The results indicate that the individuals in this study appear to have been well-adapted to their environment.

Single-year spikes in radiocarbon production are caused by intense bursts of radiation from space. Supernovae emit both high-energy particle and electromagnetic radiation, but it is the latter that is most likely to strike the atmosphere all at once and cause a surge in 14C production. In the 1990s, it was claimed that the supernova in 1006 CE produced exactly this effect. With the 14C spikes in the years 775 and 994 CE now attributed to extreme solar events, attention has returned to the question of whether historical supernovae are indeed detectable using annual 14C measurements. Here, we combine new and existing measurements over six documented and putative supernovae, and conclude that no such astrophysical event has yet left a distinct imprint on the past atmospheric 14C record.

Jaguariaíva 1 is a sandstone rockshelter located in Jaguariaíva, Paraná State, Brazil, with rock art on the surface of the walls and ceiling. A stratigraphic analysis of the soil within the shelter showed six occupational layers and a superficial disturbed layer with evidence from the end of the 19th century. The establishment of a rock-art chronology became possible using fallen painted rock sections incorporated into three sedimentary levels underlying this rock shelter. These show superimpositions of several pictures of differently sized animals, such as deer, and lattice motifs, which are generally associated with the Planalto rock art tradition. The chronological study was performed based on radiocarbon (14C) analysis of charcoal collected from six excavated subsurface archaeological contexts. The two oldest layers, associated with hunters and gatherers of the Umbu tradition, were dated to 7680–7516 cal BP and 6913–6656 cal BP. There are four occupational layers from ceramists and farmers related to the south Jê linguistic family, and linked to the Itararé-Taquara archaeological tradition: layer 3 linked to the oldest of such occupation, dated to 3058–2796 cal BP, followed by layer 4, dated to 2080–1701 cal BP. Layers 5 and 6, dated to 1995–1526 cal BP and 540–152 cal BP, respectively.

The recently completed CRONUS-Earth project broadly studied the production systematics of terrestrial in-situ cosmogenic nuclides and also incorporated an intercomparison study in which multiple labs measured various nuclides in homogenized geologic materials. Aliquots of these materials were measured in several labs for multiple nuclides, and the results combined to determine benchmark, consensus values. Results for some of these samples exhibited overdispersion, meaning that the measurements from the various labs differed by more than we would expect, given the quoted uncertainties. A traditional way to handle overdispersion is to add an extra amount to the variance of each lab. Another approach is to use a method that identifies potential outliers and then gives the outliers less weight in determining the final answer. A group of such methods is based on Bayesian thinking; one relatively simple member of this group was first proposed by Press (1997). We review the Press method and then apply it to the CRONUS data sets. We compare these results to those obtained by the added variance method and discuss the implications.

We investigated age estimation of persons using 45 Japanese human teeth that consisted of mainly the third molar. We measured the radiocarbon content in tooth enamel hydroxyapatite from the crown as well as those in collagen and bioapatite in the root of the same tooth. Age estimations from tooth enamel apatite yielded an absolute age shift of 1.7±1.4 yr from the true age. This value suggests that estimating the age of Japanese people from tooth enamel is as accurate as the previous studies conducted in Europe and the USA. The 14C analysis of roots suggested that bioapatite is formed slightly later than collagen in the same tooth roots. The appropriate formation age ranges suggested by the tooth enamel analysis can be optimized and confirmed by using the additional F14C values of the root samples. We also noticed a characteristic trend of enamel δ13C values in comparison with the formation ages of the crowns of the teeth. The δ13C value tends to increase gradually from –13.0‰ to –11.5‰ from the 1960s to the 1970s, probably being caused by changes in the Japanese diet. This trend may support the selection of proper tooth formation age as supplemental data in addition to 14C content analyses.

The Late Quaternary climate in Amazonia is an issue still open to debate, with hypotheses varying from alternate dry and wet episodes to stable climate with undisturbed rainforest. We approach this question using δ13C, C/N, and, to a lesser extent, δ15N from deposits derived from four cores, with the results combined with published pollen data from two of these cores. These data were analyzed within the context of radiocarbon dating, which revealed ages ranging from 42.8–41.8 to 2.3–2.2 cal ka BP. Fluvial channel and floodplain deposits with freshwater phytoplankton recorded a trend of wet climate with dry episodes before ~40 cal ka BP, followed by humid and cold climate until the Last Glacial Maximum, with intensified aridity towards the end of the Late Pleistocene. Peaks of increased contributions in C4 land plants in the mid- to late Holocene were not synchronous and have no correspondence with Amazonian Holocene dry episodes, being due to sedimentary processes related to fluvial dynamics during the establishment of herbaceous fields on abandoned depositional sites. Thus, the climate remained wet in the Holocene, which would have favored the expansion of the Amazonian rainforest as we see today.

In this work we explore the radiocarbon (14C) signal as an independent tool to assess the year of formation of individual tree rings of tropical species in northern Brazil. Three different species were analyzed in this work: Dipteryx magnifica, Enterolobium maximum, and Hymenolobium petraeum. The studied samples are from the stem of only one individual of each species, all cut down in 2008 in Porto Trombetas, Pará, Brazil. Individual tree rings were identified based on wood anatomy and they were counted from bark to pith. Several rings were selected for 14C analysis in order to cover the overall shape of the 14C atmospheric bomb peak (after 1955). The 14C content was measured at Laboratory of Radiocarbon, Universidade Federal Fluminense (LAC-UFF). Results are compared with the Southern Hemisphere 14C atmospheric calibration curves. For E. maximum and H. petraeum the 14C signal exhibits an overall good match with the SH zone 3 and suggests annual seasonality in the growth-ring formation. These species offer suitable characteristics for dendrochronology. The D. magnifica shows mismatches in the 14C measurements that are likely a result of difficulties in identifying ring boundaries with certainty. Additional techniques may be helpful to disentangle the origin of this discrepancy.