Only a limited number of radiometric dates for the Final Palaeolithic and the first half of the Mesolithic are available from the southeastern Baltic. This paper presents eight new Late Pleistocene/Early Holocene radiocarbon accelerator mass spectrometry (14C AMS) ages of osseous artifacts housed at the Kaliningrad Regional Museum of History and Art. These artifacts include one piece of worked reindeer (Rangifer tarandus) antler, three axes of the so-called Lyngby type, one bone point, one uniserial harpoon, one so-called bâton percé antler shaft, and one slotted bone. All the samples were successfully dated and yielded five Late Pleistocene and three Early Holocene ages, including the hitherto earliest age for human occupation in the Eastern Baltic. The dates include not only a surprisingly early date for a bone point (for this region), but also some dates that contradict expected ages based on traditional typological assessment. Our study significantly adds to the still small number of existing absolutely dated artifacts from the region and proposes new ways of viewing the Final Palaeolithic and Early Mesolithic chronology in the southeastern Baltic.

The Upper Paleolithic open-air site Sungir is located in the central Russian Plain. The blank production of the lithic industry is characterized by parallel reduction with flakes being the main blank type. The tool assemblage has two components: archaic types (Mousterian-like) on the one hand and Upper Paleolithic types on the other. The available data does not allow for a confident determination of the chronological position of the Sungir site, nor does it enable researchers to distinguish different stages of human occupation. The horizontal distribution of the dated samples demonstrates the almost complete absence of radiocarbon (14C) dates for household features identified at the site (fireplaces, fire and ritual pits, large accumulations of bones, etc.). In addition, the vertical distribution of 14C dates in the rather thick cultural layer points to the exposure of the site to solifluction.

Hala Sultan Tekke is a large Bronze Age city located on the southeastern littoral of Cyprus. The city flourished from approximately 1650 BC to 1150 BC according to the archaeological evidence. Since 2010, Swedish excavations have exposed four new city quarters (CQ1–4) with three occupational phases, the 14C dating of which is of highest importance also for other contemporaneous cultures. The finds demonstrate vast intercultural connections in the Mediterranean and even with southern Scandinavia. In 2014, roughly 500 m to the east of CQ1, one of the richest cemeteries on the island was discovered. According to the archaeological evidence, the finds from the city date mainly to the 13th and 12th centuries BC. However, many of the wealthy tombs and the offering pits from the cemetery are considerably older with the oldest finds dating to the 16th century BC. This raises the question where the city quarters belonging to the oldest finds from the cemetery are situated. The radiocarbon (14C) dates from Hala Sultan Tekke have much influence on the dating of related sites because of numerous imports from a vast area. We present here new 14C data obtained in the course of the current excavations, which add to sets of already existing data.

This research investigates two factors influencing the ability of tree-ring data to provide accurate 14C calibration information: the fitness and rigor of the statistical model used to combine the data into a curve; and the accuracy, precision and reproducibility of the component 14C data sets. It presents a new Bayesian spline method for calibration curve construction and tests it on extant and new Southern Hemisphere (SH) data sets (also examining their dendrochronology and pretreatment) for the post-Little Ice Age (LIA) interval AD 1500–1950. The new method of construction allows calculation of component data offsets, permitting identification of laboratory and geographic biases. Application of the new method to the 10 suitable SH 14C data sets suggests that individual offset ranges for component data sets appear to be in the region of ± 10 yr. Data sets with individual offsets larger than this need to be carefully assessed before selection for calibration purposes. We identify a potential geographical offset associated with the Southern Ocean (high latitude) Campbell Island data. We test the new methodology for wiggle-matching short tree-ring sequences and use an OxCal simulation to assess the likely precision obtainable by wiggle-matching in the post-LIA interval.

Accurately dating when people first colonized new areas is vital for understanding the pace of past cultural and environmental changes, including questions of mobility, human impacts and human responses to climate change. Establishing effective chronologies of these events requires the synthesis of multiple radiocarbon (14C) dates. Various “chronometric hygiene” protocols have been used to refine 14C dating of island colonization, but they can discard up to 95% of available 14C dates leaving very small datasets for further analysis. Despite their foundation in sound theory, without independent tests we cannot know if these protocols are apt, too strict or too lax. In Iceland, an ice core-dated tephrochronology of the archaeology of first settlement enables us to evaluate the accuracy of 14C chronologies. This approach demonstrated that the inclusion of a wider range of 14C samples in Bayesian models improves the precision, but does not affect the model outcome. Therefore, based on our assessments, we advocate a new protocol that works with a much wider range of samples and where outlying 14C dates are systematically disqualified using Bayesian Outlier Models. We show that this approach can produce robust termini ante quos for colonization events and may be usefully applied elsewhere.

To resolve an inconsistency around AD 1895 between radiocarbon (14C) measurements on oak from the British Isles and Douglas fir and Sitka spruce from the Pacific Northwest, USA, we measured the 14C content in single-year tree rings from a Scots pine tree (Pinus sylvestris L.), which grew in a remote location in Saltdal, northern Norway. The dataset covers the period AD 1864–1937 and its results are in agreement with measurements from the US Pacific coast around 1895. The most likely explanation for older ages in British oak in this period seems to be 14C depletion associated with the combustion of fossil fuels.

This article provides a summary and in-depth analysis of all existing radiocarbon (14C) dates for the Afanasyevo Culture of the Paleometal period. The previous “long” chronology of the culture was widely criticized and contradicted many archaeological observations. The exceedingly wide ranges of the liquid scintillation counting (LSC) dates from bone samples produced in several laboratories and the systematically older ages for the wood/charcoal samples finally reveal the shortcomings of the conventional “long” chronology. From accelerator mass spectrometry (AMS), the Afanasyevo burials of the Altai are dated to the 31st–29th century BC, whereas those of the Middle Yenisei Region to the 29th–25th century BC, which confirms the relatively earlier age of the Altai monuments. The “short” chronology removes the incompatibility of deriving the Afanasyevo Culture from the Yamnaya Culture, which previously appeared “younger” than the Afanasyevo, and also contradictions with the archaeological data. It also explains the small number of sites, the small size of the cemeteries and the lack of the internal periodization. We can now clearly move, from the earlier understanding that the Afanasyevo chronology is too broad, towards a different perception. The new AMS dates only represent a “core” for the Afanasyevo chronology, which cannot be narrowed down, but could be slightly expanded over time.

High-resolution sediment chronologies with the best possible time control are essential for comparing palaeoecological studies with independent high-precision climatic, archaeological or historic data in order to disentangle causes and effects of past environmental, ecological and societal change. We present two varved lake sediment sequences from Moossee and Burgäschisee (Swiss Plateau) that have chronologies developed with Bayesian models and radiocarbon (14C) dating of terrestrial plant macrofossils extracted from sediment samples with constant age ranges. We illustrate the potential of high-resolution 14C dating for the construction of robust, high-precision sediment chronologies. The mean 2σ age uncertainties were reduced to±19 cal yr for Moossee and to±54 cal yr for Burgäschisee over the entire period of 3000 cal yr, while 2σ uncertainties of only±13 cal yr and±18 cal yr respectively, were achieved for shorter time intervals. These precisions are better than or comparable to those of previous varve studies. Our results imply that a sophisticated subsampling strategy and a careful selection of short-lived and well-defined terrestrial plant remains are crucial to avoid outlying 14C ages. A direct linkage between palaeoeological studies with dendrochronologically dated, local archaeological sites as well as a precise comparison with high-resolution climate proxy data have become feasible.

The accelerator mass spectrometry (AMS) center at Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, Bucharest, is based on the latest-generation 1 MV Tandetron® accelerator, produced by High Voltage Engineering Europa (HVEE), The Netherlands. The AMS center became fully functional at the start of 2013, and at the end of 2015 the laboratory established the RoAMS international code and it was added to the list of AMS laboratories maintained by Radiocarbon journal. An important aspect in the establishment of a new AMS laboratory is the declaration and documentation of the adopted protocols and to demonstrate the reliability and reproducibility of the measurements in comparison to internationally recognized reference materials. In this paper, we present the dating results on the Sixth International Radiocarbon Intercomparison (SIRI) samples that were pretreated, graphitized, and measured in our laboratory. The newly developed sample preparation laboratory can handle sample materials as (1) organic materials, (2) wood, (3) bones, and (4) carbonates. The results of our measurements are in very good agreement with the SIRI consensus values and confirm the reliability of our sample preparation laboratory and also the good performance of the HVEE AMS system. The blank levels for the SIRI materials are 0.277±0.045/0.333±0.046 percent modern carbon (pMC) for wood samples, 0.441±0.038 pMC for bone collagen, and 0.239±0.030 pMC for carbonate materials, considering an average mass of 1 mg sample graphite.

Each of the laboratory intercomparisons (from ICS onwards) has included wood samples, many of them dendrochronologically dated. In the early years, as a result of the majority of laboratories being radiometric, these samples were typically blocks of 20–40 rings, but more recently (SIRI), they have been single ring samples. The sample ages have spanned background through to modern. In some intercomparisons, we have examined different wood pretreatment effects, in others the focus has been on background samples. In this paper, we illustrate what we have learned from these extensive intercomparisons involving wood samples and how the results contribute to the global IntCal effort.

Increasing demands for small-scale radiocarbon (14C) analyses required the installation of a “SO-110 B” type ion source (HVE Europa B.V.) at our 6 MV Tandetron AMS (HVE) dedicated for the direct injection of CO2 using either the gas injection system (GIS) from Ionplus AG or a EuroVector EA 3000 elemental analyzer (EA). We tested both systems with multiple series of 14C-free and modern standards (2.5–50 µg C) combusted in quartz ampoules or EA containers and were able to quantify exogenous C introduced. In EA-GIS-AMS analysis exogenous C is mainly derived from the EA sample containers. Blank values for 50 µg C combusted in solvent-cleaned tin (Sn) vessels were 0.0127 ± 0.0012 F14C (boats) and 0.0090 ± 0.0010 F14C (capsules), while they were much higher for thermally cleaned silver (Ag) capsules. The processing of gas samples for GIS-AMS yields similar blank values corresponding to 0.30 ± 0.08 µg exogenous C with 0.93 ± 0.23 F14C consisting of 0.28 µg C modern and 0.02 µg C fossil C. The combustion of larger amounts of blank material (1 mg C) in a single quartz tube split into aliquots gives lower blanks (0.0064 ± 0.0008 F14C; 50 µg C). Thus, 14C analysis of small, gaseous samples is now possible at CologneAMS.

We examined the radiocarbon (14C) reservoir effect in Lake Kutubu using tephrochronology and terrestrial plant material to deliver a precise age-depth profile and sedimentation rates for this lake. Based on the presence of two tephra horizons (Tibito and Olgaboli), we found a reservoir age offset in sediments of between 1490 and 2280 14C yr using the sediment ages derived from the lead-210 (210Pb) dating method. The live submerged biological samples collected exhibited a higher reservoir age offset than the sediment. This is most likely a result of delayed transport of “bomb” 14C from the atmosphere to aquatic and sedimentary system. The 14C reservoir effect increased with distance from the lake inlet and also decreased with depth. Dissolution of 14C-depleted carbon from surrounding limestone and direct in-wash of old soil or vegetation remnants from the catchment are the most likely causes of the 14C reservoir effect. Based on limestone areas mapped in Papua New Guinea, we indicate lakes which may be subject to a significant 14C reservoir effect. The results of this study demonstrate the magnitude of the 14C reservoir effect in lakes and provide insights to the correct interpretation of past environmental and archaeological events in PNG.

A fully automatic continuous-flow gas injection interface was built to couple an elemental analyzer with a MICADAS accelerator mass spectrometer (AMS) as a low-cost option that does not require an absorber trap for CO2 injection. The complication of the variable ion current during gas injection can be overcome by understanding and controlling the mass flow-dependent ionization yield. The time-varying CO2 concentrations and carbon mass flows are estimated with a mathematical model in order to investigate their relationship with the abundant isotope (12C–) signal. This model is based on a complete CO2 diffusion equation and instantaneous mass flow. It shows a good agreement between model calculations and the measurements. A reversible suppression of the formation of ions occurs, if the carbon mass flow exceeds 2.0–2.3 µg C/min. This result repeats for different injection capillaries and for different carrier volumetric flow rates.

Two tree-ring series, one from a high-latitude pine tree (located in northern Scandinavia) and one from a mid-latitude oak tree (located in eastern Germany) were analyzed for radiocarbon (14C) at annual resolution. The new records cover the calendar date ranges 290–460 AD and 382–486 AD, respectively, overlapping by 79 yr. The series show similar trends as IntCal13. However, some significant deviations around 400 AD are present with lower Δ14C (higher 14C ages). An average offset between the two new series and IntCal13 of about 20 years in conventional 14C age is observed. A latitudinal 14C offset between the tree sites in central and northern Europe, as would be expected due to the relatively large spatial distance, is not recorded, however. Periodic changes in the 14C records are resolved that can be attributed to the “11-year” solar cycle (Schwabe cycle) with cycle length from 9 to 11 years. The magnitude of changes in Δ14C due to the solar cycle is between 1.5 and 3‰. Since solar cyclicity is only partially synchronous between the two new series, reasons for asynchronicity are explored.

A collision-radiation model of the solid sample cesium sputter ion source led to the rediscovery of anion production by ion-pair production. The model revealed physical processes that may produce high current outputs from such sources and suggested new ways of obtaining high outputs at lower heat and conductive stress to the source. Primary among these solutions is the electron excitation of primary Cs0 recycled from the sample to provide states that efficiently create chosen anions. Here we look at how the processes might apply to gas-fed ion sources.