Slack-water deposits are archives of paleoflood frequency, magnitude, and provenance. In the eastern Himalaya, deposits along the Siang River document Quaternary outburst megafloods originating from southeastern Tibet. Here we present new observations of slack-water deposits within aggradational terraces of the Siyom River, the Siang’s largest tributary. Terrace stratigraphy reveals distinct, regionally extensive sedimentary facies including laminated sands, clays, and detrital organic-rich deposits consistent with slack-water deposition from temporarily impounded waters. Radiocarbon dates from clay and organic horizons range from 34,020 to 10,630 cal yr BP, overlapping with age constraints for Tibetan paleolake deposits. Detrital zircon (U-Th)/Pb geochronology confirms a local source for the underlying fluvial facies, whereas event-deposit silts contain young zircons derived from Tibet, supporting their interpretation as megaflood deposits. This evidence, combined with the deposits’ temporal overlap with Tibetan paleolakes and distinctive slack-water sedimentology, demonstrates that event facies formed through megaflood backflooding sourced from southeastern Tibet. The results point to the likelihood of similar deposits in other tributaries, providing a framework for regional investigation. Our findings further show that megafloods in steep terrain can produce substantial deposition and terrace formation tens of kilometers upstream in tributaries—far beyond the main stem floodway—revealing an overlooked geomorphic imprint of extreme floods.

Oil contamination in estuarine and coastal ecosystems presents major challenges for environmental monitoring due to the complex mixture of organic matter from biogenic and petrogenic sources. This review synthesizes recent advances and limitations in the combined use of carbon isotopes δ13C and Δ14C to trace petroleum contamination in marine sediments. Sixteen empirical studies were analyzed to evaluate the effectiveness of this dual-isotope approach in identifying fossil carbon, estimating its degradation state, and assessing its environmental persistence. While δ13C provides insights into organic matter sources and transformation, Δ14C offers a sensitive tracer for detecting fossil carbon inputs, even in low concentrations or mixed matrices. The review highlights how their integration strengthens source attribution and enhances the resolution of hydrocarbon monitoring in dynamic coastal settings. An exploratory typology based on Δ14C and Fm is proposed to semi-quantitatively classify contamination severity and support cross-study comparisons. Despite its potential, the approach faces challenges such as high analytical costs, limited laboratory access, and a lack of methodological standardization. Future efforts should focus on integrating compound-specific isotope analysis, expanding applications in mangrove ecosystems, and refining interpretative models to improve the forensic utility of carbon isotopes in oil spill investigations. This review contributes to the systematization of isotopic methods in environmental forensics and reinforces their role in tracing petroleum-derived carbon in sensitive coastal environments.

Burial mounds, or kurgans, are a widespread archaeological feature in ancient Eurasia. In the South Caucasus, the Kura-Araxes (KA) culture adopted these funerary structures to express horizontal social ideology through collective inhumations. KA communities also constantly re-engaged with the dead through the regular reopening of burials, contributing to a rich organic archive that relates to episodes of funerary manipulation. This article reports on the results of a radiocarbon wiggle-match obtained from a semi-burnt branch of Juniperus sp. associated with Kurgan 8 at Uzun Rama (Ganja, Azerbaijan). This structure yielded evidence of burial activity during the KA I phase (ca. 3500–3000/2900 BCE) and the post-KA, the “Early Kurgan” period (ca. 2500–2000 BCE), and the Late Bronze Age (ca. 1500–1150 BCE). The sample came from a wooden structure constructed and then burnt in the ritual closure of the kurgan by fire, marking the final stage of its KA use. The results of the wiggle-match allowed us to produce a close estimate for the felling of the branch, thus providing a refined Terminus Post Quem (TPQ) for the construction of the wooden structure itself and its use within 3204–3174 BCE. These results shed light on finer temporal resolution of burial history not just pertaining to funerary sequences, but also in terms of social engagement with visible landmarks and long-term cultural or generational memory. The results correlate with broader trends observed in other KA kurgans and settlements excavated along the Kura basin, pointing at large-scale landscape (or even historical) reconfigurations across the Kura-Araxes world.

The prehistoric cultural material at the Lodoso Site, a Middle Archaic to Late Prehistoric campsite near Driscoll, Texas, is dominated by irregularly shaped heat-hardened fragments of earth called burned clay objects (BCOs). These artifacts are a common component of coastal plain archaeology in Texas and elsewhere in the state. Many such sites, especially those situated in sandy soils, do not preserve charcoal well, which renders dating the occupations challenging. The clayey matrix of the Lodoso Site does preserve charcoal, which presents an opportunity to assess the suitability of luminescence dating of burned clay objects by thermoluminescence (TL) and optically stimulated luminescence (OSL), and directly compare those results with charcoal collected from the same excavation provenience, as well as OSL dating of the sedimentary matrix. The TL and OSL results generally track together well but are consistently slightly older than charcoal collected from the same level. The charcoal dates suggest the midden formed between approximately 1500 and 2300 years ago, whereas the luminescence ages suggest formation occurred between 2000 and 3000 years ago. Where the luminescence ages occur out of stratigraphic order, so do the paired charcoal samples, indicating that this is a result of pedoturbation. The results of both radiocarbon and luminescence dating indicate that the midden is a diachronic feature resulting from use over a prolonged period rather than the product of a single burning event.

The reduction of anthropogenic methane emissions is a priority due to its potent global warming potential. Radiocarbon (14C) can distinguish between methane from natural biogenic and fossil fuel sources, however, the analysis of methane 14C by conventional accelerator mass spectrometry (AMS) techniques is demanding. At SUERC, a prototype positive ion mass spectrometer (PIMS) is set up to directly analyze 14C in methane with minimal sample preparation. Methane gas was mixed with a stoichiometric amount of oxygen in an open split and admitted directly into the source. A series of modern, blank and unknown methane samples were clearly distinguishable by their 14C/13C raw ratios. The collision cell gas flowrate was then increased to lower the limit of detection. We obtained a corrected 14C/13C raw ratio of less than 2 × 10–13 for blank fossil methane which corresponds to a radiocarbon age greater than 50 kyr. Modern biogenic methane had a measured 14C/13C raw ratio approaching 1 × 10–10 which is consistent with the nominal value of contemporary atmospheric methane. These first results indicate that PIMS has the potential to be a valuable new analytical technique for screening the 14C content of biogas and in climate research studies.

We present a short database of the mole fraction of CO2 and 14CO2 in atmospheric air samples from an urban area in Gliwice, Silesia, Poland. The research covered a period from August 2023 to July 2024. A new laboratory air sampler stand was established to monitor carbon dioxide levels in Gliwice, giving the possibility to determine CO2 levels in the air using appropriate instruments to collect the air samples, extract CO2 from them, and thus measure carbon isotopes ratio 14C/12C. The analysis of the mole fraction of CO2 was determined using a low-cost system (CARBOCAP GMP343), while the carbon isotopes concentration was measured using MICADAS. The 14C in the air samples varied randomly from –55 to –24‰, while the monthly mole fraction of CO2 varied from 428 to 470 ppm. It has been also observed also that CO2 concentration is linked with the planetary boundary layer. The fraction of fossil of total CO2 has been estimated at the level of 2.5% during the investigated period of time. Another aim of this study was to investigate pine needles as 14C archives in a contemporary environment. The examination of the needles was based on the analysis of the similarities and differences in radiocarbon concentrations in pine needles of various ages collected in the middle of consecutive seasons, with 3 months resolution in Gliwice. The concentration of 14C in the needles was determined using a liquid scintillation counter. The mean F14C from all the samples was 99.80(70) pMC.

The suitability of marine limpet shells for radiocarbon dating may depend on potential offsets due to diet and habitat, especially with regard to grazing mollusks on carbonate substrates (Dye 1994; England et al. 2013). A previous study on one grazing limpet species on the coast of Ireland found no offsets from carbonate substrates (Allen et al. 2019), but a similar study from mediterranean coasts found significant offsets on carbonate substrates (Ferguson et al. 2011). We carried out a new study of radiocarbon and stable carbon isotopes, using multiple species of mollusks collected live from the coasts of Gibraltar and Sardinia, from both carbonate and non-carbonate substrates. The 14C results indicate that one species, inhabiting the upper shore, has a significant offset at the carbonate locations. This species, Patella rustica, has adapted to tolerate desiccation and may have biological traits that result in higher metabolic-derived carbon incorporated in its shell. The results of this preliminary study imply that selected species of grazing mollusks are suitable for radiocarbon dating, even in areas of carbonate geology.

Radiocarbon dating by accelerator mass spectrometry (AMS) requires transforming samples into graphite, a step that typically depends on liquid nitrogen and high-purity carrier gases, increasing both cost and operational complexity. We present μGRAPHILINE, a fully automated, modular combustion–graphitization line that removes these dependencies by combining dual-zone combustion with iron–zinc reduction. Performance was evaluated on more than 180 standards and reference materials targets measured on two independent AMS systems. The μGRAPHILINE consistently achieved >90% graphitization yields, stable backgrounds of ∼0.24 pMC (≈48,500 BP), and sample throughput of ∼3.5 hours per target. Reliable operation was demonstrated for a broad sample-size range, from routine 1 mg C down to ∼0.2 mg C, with ion currents sufficient for precise AMS analysis. The system’s automation, modularity, and low memory effect support improved laboratory throughput and operator efficiency. These results indicate that μGRAPHILINE provides a robust and efficient approach to radiocarbon sample preparation with broad potential applications.

This work aims to clarify the absolute chronology of the construction phases of the St. Peter and Paul Rotunda at Budeč, focusing on the erection of the rotunda and the tower. Fifteen mortar samples were taken from various structural parts, two of which also contained remnants of charcoal. The mortar samples were mechanically treated to extract a purified calcitic binder that was dated by radiocarbon analysis. The effectiveness of the sample pretreatment methodology was assessed by means of cathodoluminescence microscopy. Thin sections of mortars were characterized by polarized light microscopy. The petrographic characterization allowed for the samples to be grouped according to their binder, aggregate, and structure. This was compared with the evaluation of the calibrated dates, expected chronology known from legends, as well as with formal and stylistic analyses of the structure. The radiocarbon dating distinguished the different construction phases well, and the accuracy and reliability of the dating is discussed. The presence of silts and clays probably led to geogenic carbon contamination of the samples from the foundations, as the obtained dates are older than expected. These dating results were thus regarded as inconclusive. However, the samples from the vaulted dome of the rotunda did not show any anomalies, and the calibrated date period obtained was regarded as relevant and thus successfully dated. The dating based on the legends also fits the determined interval.

Estimates of marine reservoir corrections (ΔR) in the southeastern Arabian Sea region are limited. To better constrain the region’s marine reservoir corrections, additional pre-bomb radiocarbon records are needed. In this context, a coral core from the Lakshadweep archipelago in the southeastern Arabian Sea has been analyzed to measure its radiocarbon content. Pre-bomb radiocarbon values from the coral record are used to estimate the marine reservoir correction value of the region. The mean ΔR value of the Lakshadweep region is calculated to be –128 ± 130 yr. The comparison of available ΔR values from the Arabian Sea region shows that the mean ΔR value of the eastern Arabian Sea is significantly lower than that of the northern and western Arabian Sea. The low ΔR values from the eastern Arabian Sea likely indicate the influence of relatively 14C-enriched Bay of Bengal water in the region.

Ocmulgee Mounds National Historical Park, located in Macon, Georgia, is one of the most iconic cultural sites in the Southeast and is a Traditional Cultural Place (TCP) of the Muscogee Nation and other federally recognized Tribal Nations. Early work (1933–1941) revealed a network of earthen monuments and other features. Prior to our work, there were only two radiocarbon dates from the primary Native American occupation of Ocmulgee. Both were run in the 1960s—and only one is from the famous Earthlodge community building. These assays contributed to a general chronological assignment of the site to AD 1015. Our new dating program—including wiggle-matched radiocarbon dates from one of the timbers of this building—indicates a later construction for the Earthlodge and likely continuous occupation for other areas of the site, calling into question beliefs about Ocmulgee and its place in interpretative constructs. This work is a collaborative effort that includes Muscogee Nation, academics, National Park Service archaeologists, and private citizens. The results have implications for understanding not only the Muskogean-speaking people’s histories and their relationship to TCPs but also how we can begin to conduct archaeology in a way that strengthens descendants’ connections to ancestral homelands.

The bulk organic-matter content of near-surface sediment is widely used for radiocarbon (14C) dating, despite often containing organic carbon (OC) older than the depositional age. Low-temperature combustion can mitigate the influence of old OC, producing ages closer to the depositional age. We developed a simple method to determine the 14C age of the low-temperature (<250°C) component of bulk sediment. Sediment samples from five Arctic lakes were heated up to 400°C, revealing that at 250°C, about half of the OC combusts, leaving behind the more recalcitrant fraction. We applied this method to 64 samples from late glacial and Holocene sediment cores, analyzing 14C and % OC in two aliquots: one heated at 250°C and one unheated. The low-temperature 14C age was calculated by difference using a two-component mixing model. Accuracy was assessed by comparing ages with macrofossils from 48 samples, and reproducibility was tested using a standard reference material. Results show that low-temperature combustion yields 14C ages with an interquartile range of 115 years, and with reproducibility on par with that of macrofossil dating. On average, the ages differ by 932 years from macrofossils, compared to a 2425-year difference for conventional bulk-sediment ages analyzed in this study. Accuracy improves for samples where the proportion of residual OC after heating is low. This practical and efficient method complements macrofossil dating, supports analysis of a large number of samples, and provides insights into sedimentary carbon cycling.

Carbon occurs as organic and inorganic matter in numerous complex forms and mixtures. Thermal separation of sample mixtures (e.g. sediment or soil), coupled with radiocarbon analysis, is a valuable approach for investigating the source, residence time, or age of different carbon components. At the NEIF Radiocarbon Laboratory we have built equipment for thermally separating samples for radiocarbon analysis using ramped oxidation. The original instrumentation has been successfully tested and validated for the purpose of partitioning samples based on their temperature of thermal decomposition, and for reliable radiocarbon measurement of different sample components. However, the original configuration of our instrument has limitations; a single analysis takes 2–3 hours, and an operator must be present to manually isolate samples from the required temperature ranges. To address this, we have upgraded our ramped oxidation equipment to include computer-controlled solenoid valves. These are activated according to a user-defined sampling scheme which enables autonomous collection of thermally partitioned samples. Here, we describe the latest improvements and present thermograms showing compatibility with the previous version of our equipment. This includes measurements of the radiocarbon background of the equipment, and results for known 14C-content radiocarbon standards. These demonstrate the reliability of the new configuration of our equipment for radiocarbon measurements.

This contribution provides a chronological overview which is the result of a research programme carried out over the last few years in Normandy and which is based, among other things, on recent discoveries made in this region during developer-funded excavations. The overview looks phase by phase at the different characteristics of the Middle Neolithic in Normandy, and sets them against the wider context of the Neolithic transition of north-west France. The geographical area covered by this study encompasses the margin of the Armorican Massif in the west and the sedimentary basins between the Armorican Massif and the Seine Valley in the east. The chronology used in this study largely refers to the sequence established in France and is discussed on the basis of absolute dates (in cal BC) for the sake of transparency. The main objective of this publication is to connect the recent advances made on either side of the Channel, in particular with regard to the chronology of the various Neolithic groups. By presenting our British colleagues with the current state of research in our area of study we want to spark discussion and develop new collaboration.

The analysis of the radiocarbon age of dissolved organic carbon (DOC) is fundamental for understanding the aquatic component of the global carbon cycle, yet the technique is not routinely available at radiocarbon laboratories. This study presents validation experiments for an improved wet oxidation method for 14C-DOC analysis in a freshwater matrix. Emphasis in design protocol for the method was placed on the quantitative removal of inorganic carbon, and a background level consistent with modern accelerator mass spectrometry (AMS) radiocarbon measurements. The method utilizes a pre-oxidized potassium persulfate oxidant in crimp-sealed vials with rigorous multi-stage helium purging to achieve and maintain a sample without atmosphere carbon dioxide and the contamination of modern 14C (14C-free). Method validation of 14C-free samples are demonstrated with procedural blanks, phthalic anhydride (PhA), and an International Atomic Energy Agency Oxalic Acid standard (IAEA-C8).

Carbon-14 (14C) is an important contributor to the collective effective dose to the public due to releases from nuclear power plants (NPPs). In Sweden, only airborne emissions of 14C from NPPs are currently routinely monitored, and the existing data on waterborne 14C discharges are limited. A recent study of 14C in brown algae (Fucus spp.) in Swedish coastal waters showed higher F14C values collected at Ringhals NPP, on the Swedish west coast, than expected. Therefore, this study aimed at assessing if blue mussels (Mytilus edulis) could be used to retrospectively estimate the 14C concentration of dissolved inorganic carbon (DIC) in seawater at three sites. A method was developed to extract the fibrous layer that forms visible annual structures in the shells. All samples were analyzed with accelerator mass spectrometry and the results compared with 14C data from Fucus spp. For one of the analyzed shells (structures from 1974–1978), from the site Särdal, F14C in Fucus spp. and M. edulis agreed very well. For another shell (1972–1978), shell structures from some of the earlier years displayed up to 6% lower F14C than Fucus spp. F14C in one shell from a remote site, Båteviken, only had small annual variations (2017–2022: F14C = 1.070 ± 0.015 (1 σ)). Two shells from Ringhals NPP had higher average F14C, and a significant temporal variability (2014–2022: F14C = 1.427 ± 0.268 (1 σ)). Difficulties in unambiguous identification of the annual structures in the shells, as well as the future potential of this method, are discussed.

New excavations at Ormagi Ekhi in Georgia have revealed long-term hominin occupations during the Middle Palaeolithic (260–45 ka cal BP). Here, the authors present an overview of data from multidisciplinary analyses of the site, highlighting its potential for widening our understanding of hominin occupations in the South Caucasus.