Excavations from 2009–2010 in Armadale, Isle of Skye, Scotland, encountered a burial site with seven cists, pits containing cremation burials, a kerbed cairn, and a small stone and post circle. Twenty-one radiocarbon measurements were taken from single entities of wood charcoal, carbonized residue on pottery, and cremated human bone. A site chronology has been constructed using a Bayesian approach that considers the stratigraphic contexts and feature formation processes. The site was host to thousands of years of discontinuous human activity beginning with little understood Mesolithic and Neolithic components. Modeling estimates that mortuary activity at the site began in the Early Bronze Age in 2220–1985 cal BC (95% probability) and to have ended in 1880–1660 cal BC (95% probability). The span of activity during this burial component is estimated to be 140–520 yr (95% probability) in the primary Bayesian model and 50–470 yr (95% probability) in an alternative model. These modeling results demonstrate that human burial at Armadale was an infrequent event and further suggest that the memory of the location and social role of Armadale as a burial ground persisted throughout much of the Early Bronze Age.

Given their sheer number and evidence for long-term prehistoric occupation, atolls occupy a unique position in the peopling of the Pacific. However, they have frequently been overlooked in favor of larger islands due to a host of logistical and other issues. Once viewed as marginal environments, current research is now showing that small islands like these may have been more attractive to settlers than once thought. A new research program in Micronesia is dedicated to examining atolls to better develop baseline chronologies and investigate long-term human adaptations. As part of the initial stage of the project, we present the first radiocarbon dates (n=10) from Mwoakilloa (Mokil) atoll, which support a continuous occupation beginning between 1700–1560 cal BP (2σ). When compared to the settlement of other atoll groups in Micronesia such as the Marshall Islands—along with the nearby high volcanic islands of Pohnpei and Kosrae at approximately 2000–1800 yr ago—the dates from Mwoakilloa suggest a nearly contemporaneous or only slightly later occupation. The recovery of faunal material also demonstrates the translocation of at least two animals (Pacific rat and dog) to the island by humans that was coeval with early settlement. Additionally, there is evidence of landscape transformation in the form of a relatively large artificial mound created by debris and platform accumulation unseen elsewhere in central-eastern Micronesia, but common to atolls. These new dates reinforce the notion that Mwoakilloa and other atolls are integral to understanding prehistoric adaptations across the vast Pacific, though many questions still remain such as to the degree of interaction that occurred with nearby islands and whether settlement was continuous or intermittent through time.

We present the first radiocarbon dates of Early Iron Age sites of central Kazakhstan (in total, 24 dates for 16 recently excavated sites). Archaeologically, the sites have been attributed to the Tasmola culture of the Saka period and later Korgantas phase of the early Hun period. The new accelerator mass spectrometry (AMS) 14C dates suggest that the majority of analyzed Tasmola sites belong to the beginning of the 8th–5th century cal BC, while Korgantas dates to the 4th–2nd century cal BC. This corresponds with the latest archaeological data for the region; however, it is somewhat contrary to the traditional perception of the chronology of the Scythian period in central Kazakhstan. The new dates suggest the beginning of the Early Scythian period in the region in at least the late 9th or 8th century BC rather than 7th century BC according to the traditional approach.

Exposure age dating using in situ10Be and 26Al is a very useful technique for dating fluvial terraces. This is especially true in semiarid regions where other methods suffer from a paucity of suitable dating materials. This article describes sample preparation procedures and analytical benchmarks established at the Xi’an Accelerator Mass Spectrometry (AMS) Center for the study of in situ10Be and 26Al. Four intercomparison samples were analyzed in the study, using an improved sample preparation method. The exposure age results are shown to be in good agreement with published data, and demonstrate the reliability of the dating method. This article also presents new 10Be and 26Al results from quartz samples collected from a series of fluvial terraces from Guanshan River, along the Qilian Shan, northeastern Tibetan Plateau. The ages of three fluvial terraces from the Jinfosi site are shown to be (56.4±5.3) ka for T3, (10.7±1.0) ka for T2, and (7.2±1.0) ka for T1. The dating results are consistent with published data from the same region (10Be, 14C, and optically stimulated luminescence dating methods). A comparison of high-resolution climate records with age constraints for the terrace formation shows a close relationship between terrace formation and climate change.

Reservoir age offsets are widely used to correct marine and speleothem radiocarbon age measurements for various calibration purposes. They also serve as a powerful tracer for carbon cycle dynamics. However, a clear terminology regarding reservoir age offsets is lacking, sometimes leading to miscalculations. This note seeks to provide consistent conventions for reporting reservoir 14C disequilibria useful to a broad range of environmental sciences. This contribution introduces the F14R and δ14R metrics to express the relative 14C disequilibrium between two contemporaneous reservoirs and the R metric as the associated reservoir age offset.

The intracavity optogalvanic spectroscopy (ICOGS) method has been reported to quantify radiocarbon at subambient levels (<1 part per trillion). ICOGS uses a gas sample that is ionized in a low-pressure glow discharge located inside a 14CO2 laser cavity to detect changes in the discharge current under periodic modulation of the laser power to determine the 14CO2 concentration of the sample. When claims of detection thresholds below ambient levels were not verified by other researchers, we constructed a theoretical analysis to resolve differences between these conflicting reports and built and tested an ICOGS system to establish a lower limit of detection. Using a linear absorbance model of the background contribution of 12CO2 and data from the HITRAN database, we estimate that the limit of detection (3σx) is close to 1.5×104 Modern. By measuring a 1.5×104 Modern enriched CO2 sample in a cavity modulation ICOGS system without a clear signal, we conclude that for this system the limit of detection for ICOGS must be above 1.5×104. The implications for previous ICOGS reports are discussed.

Carson et al. (2016) have measured the optogalvanic response of an intracavity cell discharge containing carbon dioxide enriched in radiocarbon in a 14CO2 laser, and compared same to an unenriched sample. The measurement was carried out by modulating the laser wavelength while slowly tuning through the laser gain profile. The results of the measurements are claimed to “invalidate the optogalvanic method for radiocarbon detection.” A broadband linear absorption model is presented in support of this hypothesis. In fact, the experimental design was such as to minimize any possibility for 14C detection, and the model presented is not relevant to their experiment. Crucial control measurements were not carried out and the model used did not differentiate between broadband absorption spectroscopy and intracavity optogalvanic spectroscopy (ICOGS) with a narrow-band single-mode CO2 laser.

Our results, when taken alongside those of two other research groups, appear to invalidate the early positive results for intracavity optogalvanic spectroscopy (ICOGS) and its detection of radiocarbon. Daniel Murnick, whose lab published those early results, has directed a comment setting out the perceived shortcomings of our article and the reasons that the results do not constitute invalidation, as our article claims. Absent support from his own findings or published literature, his various counterclaims regarding our experimental procedure appear to constitute only his considered professional opinion and the largest confounder highlighted by our research is not even mentioned. The preponderance of documented evidence regarding ICOGS clearly supports the null hypothesis and in our opinion, nothing in Murnick’s comment indicates otherwise.