The influence of hydrochloric acid pretreatment on F14C and radiocarbon dates from dental enamel was investigated. Samples from modern equine incisors, a Roman cattle molar, and a Paleolithic woolly rhino molar were sampled and subsequently divided into five fractions. Each fraction was pretreated with a different acid solution, analyzed with Fourier transform infrared spectroscopy (FTIR), and accelerator mass spectrometry (AMS) 14C dated at the Oxford Radiocarbon Accelerator Unit (ORAU). When compared to a control date (e.g. dentine collagen), better results were observed when increased concentrations of hydrochloric acid solution were used in the chemical pretreatment. This pilot study suggests that decontamination of younger samples may be possible. However, for more fossilized samples with a high level of contamination (e.g. from the European Paleolithic), acid pretreatment under the conditions used in this study does not remove all contamination.

Lightweight concrete was widely used and mainly spread during the Roman period. This technology was used in the West Church, Umm el-Jimal, Jordan. The date of construction of the West Church is debated and different dates have been suggested based on its architectural styles and comparisons with other churches. This research aims to radiocarbon date the construction of the dome (church), archaeometrically characterize the mortar, and determine the source of the scoria. Three charcoals and two broken pieces comprising scoria from the mortar of the fallen dome and six large scoria samples from Quais cone were collected. The research used different analytical methods including accelerator mass spectrometry 14C, X-ray diffraction, petrographic microscopy, inductively coupled plasma mass spectrometry, and scanning electron microscopy-energy dispersive X-ray spectroscopy. 14C determinations dated the dome (church) to the Late Roman–Early Byzantine periods, which contradicted the archaeological data. Analytical results showed that the mortar is lime-based and hydraulic. The similarities in the mineralogical composition, macroscopic and microscopic features, and chemical composition (compared statistically) of the scoria samples and the short distance between Umm el-Jimal and the Quais volcanic cone very likely indicate that the Quais volcanic cone is the source of the scoria used in the fallen dome.

Ra’s al-Hamra 6 (RH-6) is one of the earliest stratified archaeological sites along the eastern littoral of the Arabian Peninsula. This shell midden was radiocarbon dated to the 6th–5th millennium cal BC, but the majority of the dates were obtained before the advent of accelerator mass spectrometry (AMS) 14C dating and suffer from large uncertainties. In addition, most of these dates were obtained on marine and mangrove shells and required correction for local variations from the global average marine 14C reservoir age (MRA). This proved difficult because no consensus value exists for this period in the area. Recent excavations at RH-6 offered the opportunity to redate this important site in order to precisely determine its occupation history and later use as a graveyard, and establish the marine reservoir effect for this time period. Thirty-eight samples of charcoal, shells, and human bone apatite were selected for 14C dating. Bayesian modeling of the 14C dates suggests that the formation of the shell midden spanned ~1 millennium, between the mid-6th and the mid-5th millennium cal BC. Positive and consistent ΔR values were calculated throughout the entire sequence, ranging from 99±27 to 207±43 14C yr. At the beginning of the 4th millennium cal BC, RH-6 was used as a graveyard, as suggested by the 14C dating of a shell in strict association with an individual buried at the surface of the site. 14C dating of human bone apatite allowed us to calculate that 89% of this individual’s diet derived from marine resources. This finding confirms previous observations showing the overwhelming presence of marine and mangrove-dwelling species in the faunal and charcoal assemblage, and implies a low mobility, or mobility restricted to the coast for this population during the 4th millennium cal BC.

This paper presents the first successful methods for accelerator mass spectrometry (AMS) dating of asphalt-impregnated insect chitin from the Rancho La Brea Tar Pits in southern California. A persistent problem with stratigraphic correlation at this site is that asphalt flows are characteristically intermittent and are really discontinuous, which can result in mixing fossils of quite different ages. Direct 14C dating of specimens circumvents this difficulty but requires a pretreatment method that can produce dates from relatively small samples (<10 mg) of insect cuticle, while successfully removing residual asphalt and sample preparation solvents as well as soil carbon contamination. 14C dating accuracy was verified by comparing dates on insect chitin with ages for seeds and twigs compacted during a rapid entrapment event within a separately dated skull of the Western Camel, Camelops hesternus Leidy. All dates fell within a relatively narrow range of ~40,000–44,000 14C yr BP, suggesting that such methods can be used with confidence on other insect material from this site. Insects are often superior paleoenvironmental indicators for establishing precise data points for climate fluctuations. This is because their lifecycles and present-day climate-restricted geographic distributions are well documented, and unlike migrating mammals and birds, insects offer crucial information about the local environment. Our results are therefore potentially significant for studies of paleoecological and paleoclimatic change within the Los Angeles Basin and coastal southern California, as well as reconstruction of entrapment events at Rancho La Brea.

In interpreting radiocarbon dating results, it is important that archaeologists distinguish uncertainties derived from random errors and those from systematic errors, because the two must be dealt with in different ways. One of the problems that archaeologists face in practice, however, is that when receiving dating results from laboratories, they are rarely able to critically assess whether differences between multiple 14C dates of materials are caused by random or systematic errors. In this study, blind tests were carried out to check four possible sources of errors in dating results: repeatability of results generated under identical field and laboratory conditions, differences in results generated from the same sample given to the same laboratory submitted at different times, interlaboratory differences of results generated from the same sample, and differences in the results generated between inner and outer rings of wood. Five charred wood samples, collected from the Namgye settlement and Hongreyonbong fortress, South Korea, were divided into 80 subsamples and submitted to five internationally recognized 14C laboratories on a blind basis twice within a 2-month interval. The results are generally in good statistical accordance and present acceptable errors at an archaeological scale. However, one laboratory showed a statistically significant variance in ages between batches for all samples and sites. Calculation of the Bayesian partial posterior predictive p value and chi-squared tests rejected the null hypothesis that the errors randomly occurred, although the source of the error is not specifically known. Our experiment suggests that it is necessary for users of 14C dating to establish an organized strategy for dating sites before submitting samples to laboratories in order to avoid possible systematic errors.

Evidence for aboriginal whale hunting, long thought to be a practice limited to Northwest Coast tribes in northern Washington and British Columbia’s Vancouver Island, was previously reported at the Par-Tee site on the Oregon coast between about cal AD 620 and 990. An age estimate for a humpback whale phalanx with an embedded elk bone harpoon point was based on radiocarbon dates on charcoal not directly associated with the whale bone. We present high-resolution accelerator mass spectrometry (AMS) 14C dates for purified bone collagen extracted directly from the whale phalanx and embedded harpoon point. A calibrated date for the harpoon point places the whale hunting event between about cal AD 430 and 550. The apparent 14C age of the whale bone is estimated to be 220±37 14C yr older than the marine model age at that time, consistent with values from the eastern Pacific. These new dates suggest that whale hunting took place on the Oregon coast as much as 200–500 yr earlier than previously reported and more than a millennium before historic contact in the region. Our research highlights the significance of museum collections and high-resolution AMS 14C dating for addressing a variety of issues related to ancient archaeological sites and cultures.

Converting biomass to charcoal produces physical and chemical changes greatly increasing environmental recalcitrance, leading to great interest in the potential of this carbon form as a long-term sequestration strategy for climate change mitigation. Uncertainty remains, however, over the timescale of charcoal’s environmental stability, with estimates varying from decadal to millennial scales. Uncertainty also remains over charcoal’s effect on other aspects of carbon biogeochemical cycling and allied nutrient cycles such as nitrogen. Radiocarbon is a powerful tool to investigate charcoal mineralization due to its sensitivity; here we report the results of a study using 14C-dead charcoal (pMC=0.137±0.002) in organic-rich soil (pMC=99.76±0.46), assessing charcoal degradation over 55 days of incubation. Using this method, we discriminated between decomposition of indigenous soil organic matter (SOM) and charcoal by microorganisms. SOM was the major source of carbon respired from the soil, but there was also a contribution from charcoal carbon mineralization. This contribution was 2.1 and 1.1% on days 27 and 55, respectively. We also observed a negative priming effect due to charcoal additions to soil, where SOM mineralization was repressed by up to 14.1%, presumably arising from physico-chemical interactions between soil and charcoal.

This article presents new radiocarbon evidence from the Middle Bronze Age palatial site of Tel Kabri (Israel). The final phase of the palace (Phase III) can be dated to Middle Bronze Age II, with an end date around the transition from Middle Bronze II to III or very early in Middle Bronze III. According to our 14C data, the end of Tel Kabri Phase III (and thus the transition from Middle Bronze II to III) can be dated to ~1700 BC. This date is about 50–100 yr earlier than traditional chronological models for the Middle Bronze Age propose (~1650 BC according to the traditional chronology or ~1600 BC according to the low chronology). 14C data from Tel Kabri thus add additional evidence for a higher Middle Bronze Age chronology for the Levant, consistent with recent 14C evidence from Tell el-Dabca (Egypt), Tel Ifshar (Israel), and Tell el-Burak (Lebanon).

This article presents 24 radiocarbon dates of different materials (animal and human bones, charcoal, and pottery) recovered from hunter-gatherer-fisher archaeological sites from the Salado River microregion, Buenos Aires Province, Argentina. We used a microregional design strategy, and considered the 14C dates as a group to analyze them with Bayesian statistics. This was essential to the analysis of the chronology of these shallow sites, in which the soil dynamics add the archaeological materials into the A horizon sedimentary matrix. In these types of sites, the occupational events are difficult to identify, so archaeological indicators are needed to assess the temporal contexts.

Tell Abu en-Ni‘aj, an agrarian Early Bronze IV village in the northern Jordan Valley, Jordan, provides a series of 24 accelerator mass spectrometry (AMS) seed dates spanning seven stratified phases of occupation. Bayesian analysis of these ages reveals that habitation at Tell Abu en-Ni‘aj began between 2600 and 2500 cal BC and ended just before 2000 cal BC. This sequence provides the longest radiocarbon record of occupation for an Early Bronze IV settlement in the southern Levant and pushes the beginning of the Levantine Early Bronze IV earlier than proposed previously. When integrated with 14C dates from an array of sites in the southern Levant, Egypt, and Lebanon, this evidence aligns with recent 14C-based chronologies calling for earlier ages for Early Bronze I–III, details Early Bronze IV chronology through the course of this period, and corroborates the date of the Early Bronze IV/Middle Bronze Age transition ~2000 cal BC.

Accelerator mass spectrometry (AMS) measurements of the radiocarbon content in very old samples are often challenging and carry large relative uncertainties due to possible contaminations acquired during the preparation and storage steps. In case of such old samples, the natural surrounding levels of 14C from gases in the atmosphere, which may well be the source of contamination among others, are 2–3 orders of magnitude higher than the samples themselves. Hence, serious efforts are taken during the preparation steps to have the samples pristine until measurements are performed. As samples often have to be temporarily stored until AMS measurements can be performed, storage conditions also become extremely crucial. Here we describe an assessment of this process of contamination in background AMS samples. Samples, both as pressed graphite (on AMS targets) and graphite powder, were stored in various storage conditions (CO2-spiked air) to investigate the extent of contamination. The experiments clearly show that the pressed targets are more vulnerable to contamination than the unpressed graphite. Experiments conducted with enriched CO2-spiked laboratory air also reveal that the contaminating carbon is not only limited to the target surface but also penetrates into the matrix. A combination of measurements on understanding the chemical nature of the graphitization product, combined with long-available knowledge on “adventitious carbon” from the surface science community, brought us to the conclusion that contamination is to a certain extent inevitable. However, it can be minimized, and should be dealt with by sputter-cleaning the samples individually before the actual measurement.

Expensive and time-consuming preparation procedures for radiocarbon and stable isotope analyses can be conducted on archaeological bone samples even if no collagen is preserved. Such unsuccessful preparation can lead to the partial destruction of valuable archaeological material. Establishing a rapid prescreening method for evaluating the amount of bone collagen while minimizing the impact of sampling constitutes a challenge for the preservation of archaeological collections. This study proposes and discusses a new methodology to detect and quantify collagen content in archaeological bone samples by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. A total of 42 Pleistocene to modern bone samples were selected according to their nitrogen content measured using an elemental analyzer. Comparison of collagen content estimation using ATR-FTIR and mass spectrometry reveals that some of the studied samples are contaminated by a nitrogen source coming from the burial environment. Two different FTIR calibration approaches were tested on the uncontaminated samples: peak-to-peak ratio and multivariate regression (PLS). The two approaches yield similar results with a good correlation of ATR-FTIR analyses and N wt% from 0.7 to 4wt% (R²=0.97–0.99; standard error of estimation ±0.22 to 0.25wt%). While collagen content remains difficult to detect in poorly preserved bones (less than ~3wt%), ATR-FTIR analysis can be a fast alternative for sample screening to optimize the sampling strategy and avoid partial destruction of valuable samples that do not contain enough collagen for further analysis.

Conventional radiocarbon analysis of carbonate records with accelerator mass spectrometry (AMS) is time consuming and the achievable spatial resolution is limited, because individual samples have to be taken and need to be converted to graphite for the measurement. A new laser ablation (LA) in situ sampling technique for rapid online 14C analyses of carbonate records by AMS is presented. By focusing a 193-nm ArF excimer laser on carbonate samples, carbon dioxide is generated and can directly be introduced into the gas ion source of an AMS. A dedicated LA cell for AMS was constructed in a way that combines rapid gas exchange with the capacity to carry sample specimen with maximum dimensions of 15×2.5×1.5 cm3. With the presented setup, negative carbon ion currents up to 20 µA were achieved. A low 14C background of 0.011±0.002 F14C was observed on 14C-free marble and different standard and reference materials could be well reproduced within errors. The novel technique allows scanning carbonate samples continuously over several cm per hour with achievable measurement precisions of less than 1% for modern samples. This approach allows acquiring highly spatially resolved 14C records at a far higher rate than with any currently available method.

The absolute chronology of the Kura-Araxes (KA) culture in the Southern Caucasus still represents a challenge due to the fragmentation and inadequacy of the radiocarbon record, as well as the inconsistencies in material typologies in the region. Recent archaeological fieldwork at the site of Aradetis Orgora in the Shida Kartli region of Georgia revealed four occupation levels dating to the KA II phase according to the local relative chronology. 14C samples were collected from reliable contexts and further selected according to reliability criteria, taking into account both archaeological issues and lab procedures. FTIR was applied in order to determine the preservation of charcoals and to monitor the efficiency of lab treatments on all the samples. Only accurate 14C measurements were selected for Bayesian analysis incorporating stratigraphic information. Two models were run, the second of which simulated intervals corresponding to unexcavated stratigraphy or due to a lack of samples. In this article, the available 14C dates for the KA occupation at Aradetis are presented for the first time and analyzed using Bayesian principles. The results of Bayesian modeling suggest that the occupation of the excavated KA II levels cover the period between 3040–2810 BC (simple model) or 3090–2720 BC (interval model).

Substances enriched with radiocarbon can easily contaminate samples and laboratories used for natural abundance measurements. We have developed a new method using wet chemical oxidation for swabbing laboratories and equipment to test for 14C contamination. Here, we report the findings of 18 months’ work and more than 800 tests covering studies at multiple locations. Evidence of past and current use of enriched 14C was found at all but one location and a program of testing and communication was used to mitigate its effects. Remediation was attempted with mixed success and depended on the complexity and level of the contamination. We describe four cases from different situations.

Accelerator mass spectrometry (AMS) is the most sensitive method for measuring 129I in environmental samples available today, with a detection limit of about 10–15 for 129I/127I. A drawback of the technique is the time-consuming chemical separation required to prepare AMS targets from raw samples. This step significantly limits applications requiring rapid analyses and large numbers of samples, for example, in monitoring studies associated with nuclear accidents. This work introduces a direct method for 129I measurements by AMS that does not require chemical separation. In this approach, stable iodine (127I) is added to a matrix of niobium (Nb) powder and mixed with dried raw sample. This mixture is pressed directly into a sputter target for AMS analysis. Two types of environmental samples have been tested in this work, seaweed and sediment. No anomalous behavior was noted in the Cs+ sputtering behavior of the targets prepared from these materials. The 129I/127I ratios and 129I concentrations measured by this rapid method were found to be in agreement with reported values that used a conventional AMS method for the same material. Based on our findings, we expect that such rapid measurements can be applied to a wide variety of materials, in addition to seaweed and sediment, as long as the sputtering-induced adverse effects do not prevent the stable operation of the ion source. The method is especially useful for screening large numbers of samples before more precise analyses are made.

In the Valencia region of Spain, the dominant use of natural caves for collective burials during the Late Neolithic and Chalcolithic periods has been documented. Collective burials are central to the hypothesis about social relationships in Copper Age societies from Iberia, and key to interpreting kinship-based societies. Les Llometes (Alcoi, Alicante) is one of the biggest collective burial sites existing in eastern Iberia. This article presents the direct 14C dates on 25 skeletal remains at the site. The results indicate that the site was used as a burial place from the end of the 5th millennium cal BC until the end of the 4th millennium cal BC, and is a first milestone for future studies that will shed light on the transition towards social structure through the use of a cemetery space. Moreover, this research is one of the few investigations of Late Neolithic collective burials in Iberia that comprises an extensive accelerator mass spectrometry (AMS) 14C data set of almost all the individuals reported at a single site. This case also serves to highlight the utility of revisiting materials from historic excavations by 14C dating all the skeletal remains that define the minimum number of individuals, and therefore ensuring a more complete picture of the prehistoric human record.

This study addresses the development of an absolute chronology for prominent burial sites of Inner Asian nomadic cultures. We investigate Saka archaeological wood from a well-known gold-filled Baigetobe kurgan (burial mound #1 of Shilikty-3 cemetery) to estimate its calendar age using tree-ring and 14C dating. The Saka was the southernmost tribal group of Asian Scythians, who roamed Central Asia during the 1st millennium BC (Iron Age). The Shilikty is a large burial site located in the Altai Mountains along the border between Kazakhstan and China. We present a new floating tree-ring chronology of larch and five new 14C dates from the construction timbers of the Baigetobe kurgan. The results of Bayesian modeling suggest the age of studied timbers is ~730–690 cal BC. This places the kurgan in early Scythian time and authenticates a previously suggested age of the Baigetobe gold collection between the 8th and 7th centuries BC derived from the typology of grave goods and burial rites. Chronologically and stylistically, the Scythian Animal Style gold from the Baigetobe kurgan is closer to Early Scythians in the North Caucasus and Tuva than to the local Saka occurrences in the Kazakh Altai. Our dating results indicate that the Baigetobe kurgan was nearly contemporaneous to the Arjan-2 kurgan (Tuva) and could be one of the earliest kurgans of the Saka-Scythian elite in Central Asia.

This fifth date list for the long cultural sequence in El Mirón Cave (Cantabria, Spain) reports on new radiocarbon assays for the Middle Paleolithic and Lower Magdalenian levels, ranging from about >45 to 15 uncalibrated kyr.

An in vivo grown human kidney stone was dated using the atmospheric bomb pulse. The growth period was found to be 17.6 yr for a sample size of 6 mm across. The step dissolution method was used, as one of several possibilities, to produce depositional subsamples. A noticeable dead carbon presence is detected in the modern industrialized diet, and as a consequence in human metabolites. The importance for correction when applying bomb-pulse dating is noted.