The chronology of long Upper Pleistocene loess sequences in Eurasia is based on combined pedostratigraphy and radiocarbon dating of high-quality charcoal. The accuracy of such a chronology depends on the reproducibility and precision of the 14C dates. However, certain dates may show discrepancies with regard to their chronostratigraphic context based on series of coherent dates. In order to evaluate the consistency and variation in the 14C dates obtained from small charcoal pieces, this question was tested on a set of spruce wood remains with well-preserved tree rings found in the Middle Pleniglacial loess-loam sequence of Kurtak (central Siberia). Tree-ring analysis of five fairly large wood pieces from three successive layers, dated to about 30.0, 30.8, and 32.2–32.5 ka BP previously, was done by continuous sampling of 90–150 rings on each wood piece. This enabled direct comparison of the succession of tree rings with the 14C dates. A total of 133 dates was obtained for the five wood pieces. The results show fluctuations in the 14C dates within a time range between 1000 and 2000 yr. Four possible causes for such variation will be discussed herein: (1) internal variability of the AMS dating method; (2) outliers; (3) variations in the 14C background; and (4) external factors such as past atmospheric 14C variations.

The Fijian archaeological record is segmented into a series of phases based on distinctive transformations in ceramic forms. Interpretations of the mid-sequence (∼1500–1300 cal BP) transition between the Fijian Plainware phase and the Navatu phase are contentious, with alternative explanations of population replacement versus internal processes of culture change. We present and analyze a series of Fijian Plainware and Navatu phase AMS radiocarbon dates acquired from superimposed but stratigraphically separated occupation floors at the Sigatoka Sand Dunes site on the southwest coast of Viti Levu. Employing an OxCal Bayesian sequential model, we seek to date the temporal span for each occupation as well as the interval of time occurring between occupation floors. The latter is estimated to be 0–43 calendar years at 2σ probability. The magnitude of ceramic and other differences between the Fijian Plainware and Navatu phase occupations at Sigatoka is substantive. We conclude that the abruptness of this change can be explained only by exogenous replacement at the Sigatoka site.

In the best case, radiocarbon measurements allow artificial objects to be dated with a precision of 10 calendar years when conventional wiggle-matching onto the IntCal09 calibration curve is applied. More precise dating can only be achieved by using annually resolved 14C calibration data, particularly in timespans when there are rapid changes in atmospheric 14C concentration. The recently observed jump in atmospheric 14C concentration of 1.5% between AD 774 and 775, though expected to be rare, is a good example for such a rapid change. We demonstrate by example that is possible to precisely 14C date the cutting year of a timber in the historically important and well-preserved Holy Cross chapel of the convent St. John the Baptist in Val Müstair, Switzerland.

Over 3000 prehistoric bone and antler artifacts, collected in the late 1930s from the former lakebed of Lake Lubāns, are held by the National History Museum of Latvia. This collection is remarkable not only as one of the largest known assemblages of bone implements in northern Europe, but also in terms of diversity of forms. The most elaborately worked objects include harpoons, often with two rows of barbs and spade-shaped bases, which are believed to date to the Late Paleolithic, and to be among the oldest organic artifacts ever found in Latvia. Four broken specimens were sampled in 2011 for accelerator mass spectrometry (AMS) dating, stable isotope analysis, and taxonomic attribution by ZooMS. The results support the interpretation that these artifacts were made from large cervid bones, and date all four objects to the early Preboreal (mid-10th millennium cal BC). The Lake Lubāns harpoons therefore fall in the same period as similar harpoons from Denmark, northern Germany, and Poland, although only a handful of these have been dated directly.

Much recent effort has been focused on the development of monitoring methods to calculate the percentage of biomass in the fuel used for energy generation in power plants. One possible method is based on measurements of radiocarbon concentration in combustion gases by liquid scintillation (LS) spectrometry. Fossil fuels contain no 14C due to their age. Therefore, after the combustion of such fuels, the resulting CO2 contains no 14C as well. The only source of 14C comes from the admixture of biomass containing modern carbon. 14C is a beta-emitting radionuclide with a maximum beta energy of 156 keV. There is no emission of gamma rays during decay; therefore, no possibility of gamma spectrometry exists. A difficult task thus is to validate the method and to calibrate it in agreement with the known amount of biomass in the fuel. For this purpose, a set of samples was prepared that were mixtures of hard coal and biomass with a known percentage of carbon. The oxycombustion method was applied for sample preparation in which the combustion of the fuel is done in pure oxygen; therefore, the combustion gas contains mostly CO2 and steam. The CO2 from the gas sample is then adsorbed by 3-methoxypropylamine. A known amount of this absorbent was mixed with a scintillation cocktail and measured in the LS spectrometer. In this way, a calibration curve has been obtained, allowing quantitative measurements of biomass content in the fuel.

Fifteen accelerator mass spectrometry (AMS) radiocarbon dates obtained on small subsections of archaeological and historical Crassostrea virginica (eastern oyster) shells provide a means to test for intrashell variability in 14C content in late Holocene Chesapeake Bay mollusks. Although salinity and temperature vary considerably throughout the year, the Chesapeake Bay generally lacks the strong coastal upwelling present in the eastern Pacific where intrashell 14C variability is significant. Intrashell variability in Chesapeake Bay C. virginica is between ∼60–100 14C yr, considerably smaller than the 120–530 14C yr ranges noted for shells from strong upwelling zones. As a precaution, we follow Culleton et al. (2006) and argue that large subsamples of shells across multiple growth increments are ideal for AMS 14C dating of mollusks to offset potential issues of intrashell 14C variability.

An important advance in the radiocarbon dating of archaeological material occurred in the late 1990s, with direct dating of cremated human remains. A crucial part of the argument was the demonstration that comparable results could be obtained from paired dates of charcoal and calcined bone from the same contexts. Recent studies, however, have noted the influence of carbon from the fuel sources, raising a question over the interpretation of the paired charcoal/bone dates. Here, fleshed modern animal joints were burned with “old” fuel of known age, providing experimental evidence under natural conditions, demonstrating a clear effect of the fuel source on the carbon isotopic composition of calcined bone. In most situations in which branchwood was used as fuel, dates on calcined bone should not show any significant offset, as the wood will be of a similar age to the cadaver. For cases in which old wood, coal, or peat are used as fuel, we expect an offset of some decades/centuries, potentially up to millennia. We observed, however, that the amount of 14C intake from the fuel is extremely variable (from 39 to 95%). A strong correlation between age offset and δ13C values suggests that the latter might be useful in identifying large inputs from 14C-depleted fuels. A level of caution is recommended when 14C dating calcined bone in cases where fuels with an inbuilt age may have been used in the cremation process.

This article reports temporal changes in the measured oceanic geochemical properties of the Arabian Sea and the equatorial Indian Ocean by reoccupying six stations investigated during the GEOSECS expedition in 1977 and 1978. Observed differences are interpreted in terms of plausible changes in the environment and climate that have occurred in response to natural or anthropogenic processes. The depth profiles of major parameters such as dissolved oxygen, ΣCO2, major nutrients (silicates, nitrates, and phosphates), and radiocarbon in dissolved inorganic carbon were measured during the cruises between 1994 and 1998 along with temperature and salinity. Most stations in the Arabian Sea show an increase in salinity by ∼0.2 to 0.3 salinity units in the top 400 m, whereas one station in the equatorial Indian Ocean showed a decrease in salinity by ∼0.1 units, indicating a likely change in the evaporation-precipitation (E-P) balance. The ΣCO2 increased by an average of 8 μM within the top 1200 m of the Arabian Sea. The depth profiles of nitrates and dissolved oxygen for the central Arabian Sea stations show significant variations, while only marginal changes are seen for silicates and phosphates relative to the GEOSECS data. The decrease in Δ14C of surface waters is due to the steady decrease in atmospheric 14C concentration since GEOSECS, and the Δ14C increase in subsurface waters is attributed to the downward vertical diffusion of bomb 14C interpreted in terms of atmosphere to ocean transfer and lateral advection of water masses.

The chronologic record of late Quaternary biota from central Alberta has broad implications for understanding the archaeological, geological, paleontological, and paleoenvironmental record of western North America. Radiocarbon dates on remains of Pleistocene megafauna were previously used as proxies for the advance and retreat of ice sheets across Alberta (e.g. Young et al. 1994; Dyke 2005), and are important for understanding landscape changes that likely influenced the timing of human dispersal into North America (Burns 1996). 14C records of Holocene age continue to refine our understanding of landscape change leading up to modern environmental conditions (Beaudoin 2003). Here, we report 15 14C dates from new and previously recorded sites in central Alberta, and one from just across the border within Saskatchewan (Figure 1).

Excavations in the cathedral of Tournai revealed two sepultures, which were identified by the excavators as those of bishops because of their special location in the cathedral. One burial was assigned to Baldwin I, who died in AD 1068, because (1) a ring with the inscription “BAL” was found and (2) a funeral stone with text was present on top of the grave mentioning the name Baldewinus. The second burial probably belongs to Radbot II, who was the successor of Baldwin I, and died in AD 1098. Both burials contained textiles (silk), the skeleton, a wooden pastoral staff, and human hair was still present on the skull of what was presumed to be Radbot II. All the protein-containing materials were degraded and/or contaminated. Standard sample pretreatment methods were not able to remove all the contaminants. Single and double cross-flow nanofiltration of the hydrolyzed protein-containing materials were performed. The sample quality for radiocarbon dating was improved and 14C data revealed interesting and surprising results. The 14C dates of the wooden pastoral staff and permeate femur confirm that the skeleton and tomb belong to bishop Baldwin I. The 14C dates of hair and permeate skull indicate that the skeleton may indeed belong to bishop Radbot II. The younger 14C dates of the wooden pastoral staff and silk samples indicate a postburial disturbance of the site burial during the 12th–13th century.

Accelerator mass spectrometry (AMS) was introduced at Yamagata University in 2010, including the measurement of radiocarbon. In the Yamagata University laboratory (YU-AMS), the application of 14C AMS is aimed at microdose pharmacokinetics investigation and the development of improved sample preparation techniques. The lab also measures environmental samples. With the installation of this AMS system, a new automated sample production system was installed, which is composed of an elemental analyzer, a glass vacuum line, and an isotope ratio mass spectrometer (IRMS). In this system, it is also possible to measure stable isotopes (δ13C, δ15N, and δ34S) of the sample gas using a mass spectrometer. To increase the amount of CO2 gas introduced into the glass vacuum line, the gas mass flow introduced into the MS was reduced, and the change of δ13C accompanying this reduction was monitored. The sample gas split was changed to set the glass vacuum line (GVL):isotope ratio mass spectrometer (IRMS) ratio to 5:5, 8:2, and 9:1, and δ13C was measured for each ratio. It was confirmed that there was no effect on the isotopic fractionation accompanying the change in the sample gas split ratio. To prioritize the use of gas in the production of graphite, the GVL:IRMS ratio of 9:1 was chosen for this setup. The components are connected on-line, and up to 20 samples can be processed automatically.

This article presents a set of accelerator mass spectrometry (AMS) radiocarbon dates derived from human bone within burial contexts at CA-NAP-399 in Napa County, California, USA.

Since 1994, our team has gained extensive experience applying accelerator mass spectrometry (AMS) radiocarbon analysis for mortar dating, totaling over 465 samples and 1800+ measured CO2 fractions. Several samples have been analyzed repeatedly. The research covers both Medieval and Classical archaeology. We therefore believe our experience can be helpful when developing preparation procedures for different kinds of mortars in different areas and in varying chronologies. So far, the main areas of interest have been (a) the churches of the Åland Islands (in the archipelago between Finland and Sweden); (b) the churches in the Åboland Archipelago (SW Finland); (c) sites in the Iberian Peninsula including Torre de Palma (a Roman village in Portugal); and (d) Rome, Pompeii, and Herculaneum (Italy). Most of the analyses before 2000 were hydrolized in only two CO2 fractions per sample, and reliability criteria were defined on the basis of how well the ages of the two fractions agree with each other. These criteria have proved most helpful in determining the reliability of 14C mortar analyses. Different types of mortar have been investigated, including lime mortars made both from limestone and marble, pozzolana mortars, fire-damaged mortars, and mortars based on burnt shells. Most importantly, separate lime lumps sampled from these mortars have been analyzed sporadically and recently more systematically. The research also includes different types of hydrolysis applied in the pretreatment. In addition to using 85% phosphoric acid (H3PO4), the experimental research includes tests with smaller concentrations of phosphoric acid, and tests based on 2–3% hydrochloric acid (HCl) dissolutions. To characterize the dissolution process, results are presented as age profiles of 2–5 CO2 fractions. In our experience, pozzolana mortars have been difficult to date, and HCl dissolution should be used only in special cases and in complementary tests.

Ancient carbon reservoirs in freshwater bodies have the potential to introduce ancient carbon into charred cooking residues adhering to pottery wall interiors when aquatic organisms are parts of cooked resource mixes. This ancient carbon results in old apparent ages when these cooking residues are subjected to accelerator mass spectrometry dating, the so-called freshwater reservoir effect (FRE). Roper's (2013) assessment of the FRE on 14C ages from cooking residue in the Central Plains is only the second such peer-reviewed regional assessment in eastern North America. Roper suggests that 13 of 23 14C ages on residue are too old as a result of ancient carbon from fish or leached from shell temper or old carbon introduced via maize nixtamalization. Herein, we re-assess Roper's data set of 14C ages on cooking residues and annual plants and argue that she is mistaken in her assessment of the accuracies of 14C ages from residues. This outcome is placed in the context of the larger FRE literature.

Natural textiles provide suitable material for radiocarbon dating. Short-lived organic matter is usually involved and, if 14C dating is applied to pieces that are stylistically well dated, a better understanding of 14C dating of this type of material can be gained. This study presents some examples of dating that support the stylistic dates. Repeated analyses illustrate the robustness of the standard treatment applied to the textiles.

In 2002–2003, excavations were carried out within the early Iron Age fortified settlement of Motroninskoe Gorodishche in Mielniki (central Ukraine, obl. Cherkassy). The excavations revealed relics of a charred wooden structure in the core of the earth rampart, originally forming the outside fortification line of the settlement. Dendrochronological analysis of 20 charred pieces of the oakwood from the rampart demonstrated that they all represented a single construction phase. However, the chronology produced from them spanned only 62 yr, and the attempts of dating against the European oak standards were unsuccessful. For absolute dating, radiocarbon analysis was conducted on nine samples consisting of 4–8 tree rings, relatively dated and coming from selected timbers, of which dendrochronological sequences defined the above chronology. The wiggle-matching method allowed to determine the two most plausible periods tree cutting: 665–630 or 625–520 BC. The construction date of the rampart outlines the beginning of construction of the fortification system of one of the most heavily reinforced strongholds in eastern Europe raised by the local, settled population for defense against the nomadic Scythians invading from the steppe. Taking into account historic data and other dated artifacts, it may be assumed that the first period, 665–630 BC, would be more probable. This conclusion supports the historical process (crucial for eastern Europe) of migration of the Iranian Scythians from inside Asia and settling in areas around the Black Sea.

Hart and Lovis clearly hold different views than do I about how to view incongruities in age determinations on food residue as compared to those on context dates on other short-lived materials. I explain how I came to the conclusions I drew in my earlier study (Roper 2013a) and suggest that I am evaluating my results, and those of others, by looking for patterns in the incongruities, rather than individually explaining away incongruent dates. I also briefly review some work with a collaborator being undertaken to correct the obvious problem with age-offset dates on residue.