Radiocarbon activity of dissolved inorganic carbon has been measured in the northwestern Black Sea. Both continental shelf and open-sea profiles show that surface waters are in equilibrium with the atmosphere. The observed distribution of 14C activity shows a weak contribution of the deep 14C-depleted CO2 to the photic zone. Such a distribution of 14C within the water column is unable to explain the aging of sedimentary organic matter and reservoir ages greater than 500 yr. A contribution of production by chemoautotrophic bacteria feeding on 14C-depleted methane at the boundary of the oxic and anoxic zones is a realistic hypothesis. Also, a contribution to sedimentary organic carbon estimated at <15% of the photosynthetic primary production could explain 14C reservoir ages greater than 1300 yr.

Radiocarbon (14C) dating provided New World archaeological research with the first continent-wide common chronometric scale that transcended the mostly relative site- and region-specific chronological sequences that had been assembled during the preceding century of fieldwork. 14C data continue to play a critical role in establishing a chronometric framework for the 5-century-long debate concerning the timing of the initial peopling of the New World. Other issues where 14C results have been of particular importance include the origins and development of New World agriculture and determination of the relationship between the Western and Classic Maya long-count calendar. The introduction of a third-generation measurement technology of accelerator mass spectrometry (AMS) beginning in the late 1970s has provided a means of obtaining analyses on milligram and microgram amounts of carbon permitting more detailed critical approaches to increasing the accuracy of 14C values on certain sample types—particularly human skeletal materials. It also provided a more effective means of allowing greater dating precision in situations where such data had an important bearing on the validity of inferences about the rates of cultural evolutionary change in New World societies.

In this paper, we present an overview of radiocarbon dating contributions from Groningen, concerning 9 sites from around the Mediterranean region: Israel, Sinai (Egypt), Jordan, Spain, Tunisia, and Italy. Full date lists of the 9 sites are presented. Our 14C dates are discussed in terms of present actual chronological debates. We show that all our 14C dates coherently support a “high chronology” for the Iron Age in each respective area of the Mediterranean region.

Combined analysis of paleoenvironment, 13C, 15N, and 14C in bone, including paired dating of human bone and terrestrial materials (herbivore bone, wood, charcoal, and textile) has been performed on many samples excavated from Russian kurgan graves. The data can be used for dietary reconstruction, and reservoir corrections for 14C dating of human bone. The latter is essential for an accurate construction of chronologies for the Eneolithic and Bronze Age cultures of the Caspian steppes.

We present accelerator mass spectrometry (AMS) radiocarbon dates on several organic fractions isolated from tropical guano deposits recovered from insular Southeast Asia. Differences were observed between 14C measurements made on bulk guano as well as bulk lipids, the saturated hydrocarbon fraction, solvent-extracted guano, and insect cuticles extracted from the same bulk sample. We infer that 14C dates from the bulk lipid fraction and saturated hydrocarbon fractions can be variably contaminated by exogenous carbon. In contrast, 14C measurements on solvent-extracted guano and isolated insect cuticles appear to yield the most robust age determinations.

Santa Lucía is a pottery production site dating to the Formative period (about 1600 BC to AD 200). It is located in the Cochabamba valleys of the eastern Bolivian Andes. The settlement consists of a residential area and a separate workshop area. A peripheral sector of ash mounds was used as refuse sites and burial grounds. The excavations yielded a total of 16 radiocarbon samples from all 3 sectors, which were dated at the Gliwice Radiocarbon Laboratory (Gliwice, Poland). The results from the deepest trench in the workshop sector (Trench 5) provide information for the stratigraphic sequence and help to define spatial and socioeconomic changes at around 600–500 BC with the beginning of the Late Formative or Santa Lucía III phase. The 14C dates from Santa Lucía, therefore, contribute to a better definition of the existing regional Formative period phases and finally to a better understanding of the processes during the Formative period in the south-central Andes.

Mortar as a mixture of binder and aggregate can be reliably dated with radiocarbon if the applied preparation method allows one to eliminate unburnt carbonate fragments, bearing 14C-depleted carbon and causing overestimation of 14C age. To avoid these problems, separation of specific grain-size fractions of mortar and 14C analysis of the CO2 portions collected in different time intervals of the acid-leaching reaction is usually helpful. In the present paper, we demonstrate that the rate of the leaching reaction of mortars with dense carbonate aggregate differs from that of mortars with crumbled limestone and scattered shells (e.g. of foraminifera). Verification of the obtained 14C dates against historical sources shows that for mortars rich in foraminiferous limestone, a reaction rate-based chemical elimination of “dead carbon” may appear impossible.

The results are presented of a new program of radiocarbon dating undertaken on 88 human skeletons. The individuals derived from Eneolithic to Early Iron Age sites—Afanasievo, Okunevo, Andronovo (Fedorovo), Karasuk, and Tagar cultures—in the Minusinsk Basin of Southern Siberia. All the new dates have been acquired from human bone, which is in contrast to some of the previous dates for this region obtained from wood and thus possibly unreliable due to old-wood effects or re-use of the timber. The new data are compared with the existing 14C chronology for the region, thereby enabling a clearer understanding to be gained concerning the chronology of these cultures and their place within the prehistory of the Eurasian steppes.

Radiocarbon dating has had an enormous impact on archaeology. Most of the dates are obtained using charred materials and, to a lesser extent, collagen from bones. The contexts in which charred materials and bones are found are often, however, not secure. There are 3 other datable materials that are usually in secure contexts: plaster/mortar, phytoliths, and the organic material in the ceramic of whole vessels. The plaster/mortar of walls and floors are often in very secure contexts. Phytoliths are abundant in archaeological sites and in some situations form well-defined surfaces. Whole vessels are usually found in secure contexts and their typologies are indicative of a specific period. Dating each of these materials has proved to be difficult, and solving these technical problems represents major future challenges for the 14C community. The effective use of charcoal and bone collagen for dating can also be improved by paying careful attention to the micro-contexts in which they are found, such as in clusters or as part of well-defined features. Pre-screening to identify the best preserved material can also contribute to improving the accuracy of the dates obtained. A general objective should be to have an assessment of the quality of the material to be dated so that the potentially invaluable information from outliers can be exploited.

Exploratory work was performed to investigate the feasibility of using a simplified radiometric analytical approach for determining the bioethanol content of US automotive fuels. The method involves mixing fuel samples directly with a suitable fluor. Sample preparation is extremely rapid since all conventional sample preparation steps are essentially eliminated. Results are based on the background-corrected DPM values obtained when using 10 mL of sample mixed with 10 mL of Permafluor E+. Results are also reported in terms of conventional pMC for some of the samples. Bioethanol from a dry-mill ethanol plant served as the analytical reference sample that represented a 100% bioethanol content. Using current-day bioethanol as a reference sample eliminates the need to correct for “bomb carbon.” For 1:1 mixtures of sample and fluor, the background-corrected DPM showed a linear relationship with the bioethanol concentration, indicating that the quench correction approach was effective for the variable-quench samples. Based on the analysis of E0 (pure gasoline), E10, and “E85” from local gas stations, it appears that the method has good potential for determining the bioethanol content in commercial ethanol/gasoline blends. However, a variety of potential sources of error still require investigation in order to refine the method.

Complex interdisciplinary studies carried out in the territory of the Vilnius Lower Castle, E Lithuania, were used to construct a chronological framework based on radiocarbon data and archaeological information. Bulk samples (wood and sediment) were collected from an approximately 3-m core that crossed cultural layers and underlying strata. 14C dates indicate that the underlying bed possibly formed during the 6th century AD, although no archaeological finds were discovered there. Paleobotanical (pollen and plant macrofossil) investigations reveal evidence of agriculture that points to the existence of a permanent settlement in the area at that time. The chronological data indicates a sedimentation hiatus before the onset of the deposition of the cultural layer in the studied area. The 14C dates showed that the formation of the cultural bed began during the late 13th–early 14th centuries AD, that is, earlier than expected according to the archaeological record. The ongoing deposition of the cultural beds continued throughout the middle to latter half of the 14th century AD as revealed by the archaeological records and confirmed by well-correlated 14C results. After some decline in human activity in the middle of the 14th century AD, a subsequent ongoing development of the open landscape, along with intensive agriculture, points to an increase in human activity during the second half of the 14th century AD. The first half of the 15th century AD was marked by intensive exploitation of the territory, indicating a period of economic and cultural prosperity. The chronological framework indicates that the investigated cultural beds continued forming until the first half of the 16th century AD.

There are 2 fundamental assumptions in radiocarbon dating, which were known early in the method development to be approximations, and which lead directly to the need to calibrate 14C dates:

1. 1. The rate of formation of 14C in the upper atmosphere has been constant over the entire applied 14C dating timescale (approximately the last 65,000 yr).

2. 2. The 14C activity of the atmosphere has been in equilibrium with the biosphere and ocean over the applied timescale.

While kept at the Rockefeller Museum in East Jerusalem, many Dead Sea Scroll fragments were exposed to castor oil by the original team of editors in the course of cleaning the parchments. Castor oil must be regarded as a serious contaminant in relation to radiocarbon dating. If modern castor oil is present and is not removed prior to dating, the 14C dates will be skewed artificially towards modern values. In Rasmussen et al. (2001), it was shown that the standard AAA pretreatment procedure used in the 2 previous studies dating Dead Sea Scroll samples (Bonani et al. 1992; Jull et al. 1995) is not capable of removing castor oil from parchment samples. In the present work, we show that it is unlikely that castor oil reacts with the amino acids of the parchment proteins, a finding which leaves open the possibility of devising a cleaning method that can effectively remove castor oil. We then present 3 different pretreatment protocols designed to effectively remove castor oil from parchment samples. These involve 3 different cleaning techniques: extraction with supercritical CO2, ultrasound cleaning, and Soxhlet extraction—each with their own advantages and disadvantages. Our data show that the protocol involving Soxhlet extraction is the best suited for the purpose of decontaminating the Dead Sea Scrolls, and we recommend that this protocol be used in further attempts to 14C date the Dead Sea Scrolls. If such an attempt is decided on by the proper authorities, we propose a list of Scroll texts, which we suggest be redated in order to validate the 14C dates done earlier by Bonani et al. (1992) and Jull et al. (1995).

Many lacustrine chronology records suffer from radiocarbon reservoir effects. A continuous, accurate varve chronology, in conjunction with accelerator mass spectrometry (AMS) 14C dating, was used to determine the age of lacustrine sediment and to quantify the past 14C reservoir effect in Sugan Lake (China). Reservoir age varied from 4340 to 2590 yr due to 14C-depleted water in the late Holocene. However, during the Little Ice Age (LIA), 14C reservoir age was relatively stable. According to this study, 14C reservoir age in the late Holocene may be driven by hydrological and climatic changes of this period. Therefore, special caution should be paid to the correction of the 14C reservoir effect by a unique 14C reservoir age in paleoclimatic and paleolimnological study of northwest China.

The wide availability of precise radiocarbon dates has allowed researchers in a number of disciplines to address chronological questions at a resolution which was not possible 10 or 20 years ago. The use of Bayesian statistics for the analysis of groups of dates is becoming a common way to integrate all of the 14C evidence together. However, the models most often used make a number of assumptions that may not always be appropriate. In particular, there is an assumption that all of the 14C measurements are correct in their context and that the original 14C concentration of the sample is properly represented by the calibration curve.

In practice, in any analysis of dates some are usually rejected as obvious outliers. However, there are Bayesian statistical methods which can be used to perform this rejection in a more objective way (Christen 1994b), but these are not often used. This paper discusses the underlying statistics and application of these methods, and extensions of them, as they are implemented in OxCal v 4.1. New methods are presented for the treatment of outliers, where the problems lie principally with the context rather than the 14C measurement. There is also a full treatment of outlier analysis for samples that are all of the same age, which takes account of the uncertainty in the calibration curve. All of these Bayesian approaches can be used either for outlier detection and rejection or in a model averaging approach where dates most likely to be outliers are downweighted.

Another important subject is the consistent treatment of correlated uncertainties between a set of measurements and the calibration curve. This has already been discussed by Jones and Nicholls (2001) in the case of marine reservoir offsets. In this paper, the use of a similar approach for other kinds of correlated offset (such as overall measurement bias or regional offsets in the calibration curve) is discussed and the implementation of these methods in OxCal v 4.0 is presented.

Glacier fluctuations and paleoclimatic oscillations during the Late Quaternary in Val di Rabbi (Trentino, northern Italy) were reconstructed using a combination of absolute dating techniques (14C and 10Be) and soil chemical characterization. Extraction and dating of the stable fraction of soil organic matter (SOM) gave valuable information about the minimum age of soil formation and contributed to the deciphering of geomorphic surface dynamics. The comparison of 10Be surface exposure dating (SED) of rock surfaces with the 14C ages of resilient (resistant to H2O2 oxidation) soil organic matter gave a fairly good agreement, but with some questionable aspects. It is concluded that, applied with adequate carefulness, dating of SOM with 14C might be a useful tool in reconstructing landscape history in high Alpine areas with siliceous parent material. The combination of 14C dating of SOM with SED with cosmogenic 10Be (on moraines and erratic boulders) indicated that deglaciation processes in Val di Rabbi were already ongoing by around 14,000 cal BP at an altitude of 2300 m asl and that glacier oscillations might have affected the higher part of the region until about 9000 cal BP. 10Be and 14C ages correlate well with the altitude of the sampling sites and with the established Lateglacial chronology.

Radiocarbon is by far and away the most widely used dating tool in the Late Quaternary. Hundreds of key papers rely on the method to provide absolute and relative chronological information on important topics, including the late evolution of our own species (e.g. Higham et al. 2006a) and the timing and nature of abrupt climatic changes during the last glaciation (Lowe et al. 2001). Calibration of 14C determinations is an essential part of the dating process, and the implications of calibration can lead to significant differences in the interpretation of important processes (Blockley et al. 2006). Any development that enhances the accuracy, precision, or time coverage of the calibration curves is therefore to be welcomed. Since the early 1980s, there has been periodic publication of carefully vetted data in the form of internationally recognized consensus calibration curves that have allowed 14C users to convert their raw 14C determinations into calendar ages (Klein et al. 1982; Stuiver and Reimer 1986, 1993; Stuiver et al. 1998; Reimer et al. 2004). In the beginning, the basis on which this was done was easy to understand, 14C measurements were made on tree rings and the absolute calendar age came from counting annual growth rings. Although not without its complexities, the terrestrial tree-ring approach remains the most certain method and is at the heart of calibration process in the period 0–12.4 cal kyr. However, for periods beyond the limit of the tree-ring sequences the situation was significantly more problematic, and at times, even controversial.

A celebration is in order: the journal Radiocarbon is now a mature 50 years without drastic changes in its identity. There have been, of course, additions in terms of specific isotopes (it is now an international journal of cosmogenic isotope research), but the 14C content is still very extensive. The triannual offshoots, conference proceedings (started in 1980), and calibration issues (the first in 1986) testify to the strength of the 14C component.

Recent comparative studies have proven the validity of radiocarbon dates of cremated bones. The issue of sample contamination has, however, been overlooked in most studies. Analyses of cremated bone samples has shown that in some cases, cremated bones are contaminated. This contamination is more distinct near the surface of the bones and depends on the compactness of the cremated bone as well as on the site conditions. δ13C is not a good estimator to discriminate between contaminated and uncontaminated bones. An acetic acid pretreatment is the most appropriate method to clean samples, but it is better to remove the surface and to avoid cremated bones that are not entirely white (cremation temp. <725 °).

The general method currently used to analyze radiocarbon data (y) is conditional on the standard deviation (σ), reported by 14C laboratories, which reflects the uncertainty in the dating process. This uncertainty is measured through a series of empirical as well as theoretical considerations about the dating process, chemical preprocessing, etc. Nevertheless, σ is assumed as known in the statistical model for 14C data used since the dawn of the discipline. This paper proposes a method for the analysis of 14C data where the associated variance is taken as the product of an unknown constant α with the sum of the variance reported by the laboratory σ2 and the variance of the calibration curve σ2(θ) (that is, an unknown error multiplier). Using this approach, assuming that the 14C determination y arises from a Normal population and that, a priori, α has an inverse gamma distribution InvGa(a, b), the resulting dating model is a t distribution with 2a degrees of freedom. The introduction of parameters a and b allows a robust analysis in the presence of atypical data and at the same time incorporates the uncertainty associated with the intra- and interlaboratory error assessment processes. Comparisons with the common Normal model show that the proposed t model produces smoother posterior distributions and seem to be far more robust to atypical data, presenting a simpler alternative to the standard 14C outlier analysis. Moreover, this new model might be a step forward in understanding and explaining the otherwise elusive scatter in 14C data seen in interlaboratory studies.