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Ramped pyrolysis radiocarbon dating was carried out on lime lumps from what was believed to be the oldest remains of Turku Cathedral, Finland, the first sacristy. Lumps extracted from bulk mortar from five sampling locations were analysed. For each sample, 5–6 fractions of CO2 from different temperature fractions were radiocarbon dated.One of the five samples exhibited significant contamination for its lowest temperature fractions. For the remaining samples, the age-temperature profiles were well-behaved, exhibiting a plateau of dates that were in statistical agreement and indicative of samples where only a single carbonate source (lime binder from the construction phase) is contributing to the radiocarbon dates. For each of the five samples, the combined radiocarbon age resulted in a calibrated age with a large probability distribution mode (typically > 85% probability) in the late 13th century AD. Combining the radiocarbon dates from all five samples (21 fractions in statistical agreement, χ2-test: df = 20, T = 7.1, 5% = 31.4) provided an age of 709 ± 11 yr BP and a calibrated age of 1276–1296 cal. AD (95.4%). This result finds excellent agreement with historical sources, previous mortar dating work, and a single radiocarbon date on organic material also embedded in some of the bulk mortar.The results demonstrate that ramped pyrolysis, applied to well-selected lime lumps, is (A) a useful diagnostic tool for establishing how reliable a sample is and (B) an accurate, precise, and repeatable technique for radiocarbon dating mortar. The results further confirm that Turku Cathedral's first sacristy was constructed from stone and mortar in the late 13th century AD.Additionally, using Turku Cathedral sacristy as a case study, two Bayesian models were presented to illustrate how, in general, mortar dating and Bayesian statistics might, in future, be applied to examine building construction dynamics for the case of (chronologically) ordered or unordered mortar derived radiocarbon dates.

Geophysical investigation of a former convent graveyard for conversion to a community centre identified an unrecorded, unmarked burial below a later burial. Archaeological excavation confirmed the presence of skeletonized human remains, considered by police as a possible clandestine burial. Mortuary examination indicated the remains belonged to a mature adult female. To determine whether the deceased could be a recorded missing person, radiocarbon dating was undertaken on a femur and a rib bone. This is not always straightforward, and results showed two possible ages due to intercepts on either side of the nuclear weapons testing spike in atmospheric 14C; however, the later dated burial allowed us to constrain the date of a rib to CE 1959. This study demonstrates that dating a second tissue with a longer turnaround time, such as a femur, can help to constrain which side of the bomb spike is most probable. This paper documents in one work the search, scene and sample and then advances this to resolution by anthropological analysis and radiocarbon dating of human remains.

Caves containing perennial ice deposits make up a little-known, but emerging part of the cryosphere under increasing scrutiny from the scientific community. M-17, a sag-type ice cave opening at 1879 m asl in the Tolminski Migovec massif of the Julian Alps (NW Slovenia) contains a perennial underground ice deposit whose paleoclimate sensitivity is poorly understood and whose longevity under current climate change is at risk. The past mass balance of this cave is constrained using wood macro-remains embedded in ice. Accelerator mass spectrometry radiocarbon dating of 18 wood samples embedded in ice provides the largest currently available dataset for a subterranean ice deposit in the southern European Alps. The reconstructed chronostratigraphy reveals three main phases of likely positive ice balance around 900–1100 AD, 1200–1300 AD, and 1700–1800 AD, as well as a period of negative mass balance around 1300–1400 AD. The onset of cave glaciation is deemed to have occurred no later than about 900 AD, with evidence of overall positive ice mass balance during multi-decadal periods characterized by cooler-than-average summers and wetter-than-average springs. Conversely, negative mass balance is recorded during a period warmer-than-average summers and dry springs. The cave has experienced ice mass loss since its discovery in the 1980s.

In this paper we evaluate the extent of freshwater reservoir effects (37 samples across 12 locations) and present new data from various archaeological sites in the Eurasian Steppe. Together with a summary of previous research on modern and archaeological samples, this provides the most up-to-date map of the freshwater reservoir offsets in the region. The data confirm previous observations highlighting that FREs are widespread but highly variable in the Eurasian Steppe in both modern and archaeological samples. Radiocarbon dates from organisms consuming aquatic sources, including humans, dogs, bears, aquatic birds and terrestrial herbivores (such as elk feeding on water plants), fish and aquatic mammals, as well as food crusts, could be misleading, but need to be assessed on a case-by-case basis.

In the late 1950s it was recognized that levels of atmospheric radiocarbon (14C) had not been constant over time. Since then, researchers have sought to document those changes, initially through measurements of known age tree rings and more recently using other archives to create curves to correct or calibrate radiocarbon ages to calendar ages. This paper highlights some, but by no means all, of the efforts to create and extend radiocarbon calibration curves.

The Quaternary Isotope Laboratory (QIL) at the University of Washington was launched in 1969 and directed by Minze Stuiver until his retirement in 1998. Here we review some of the scientific work undertaken in the QIL and the memories of some of Minze’s former students and colleagues.

In this paper we discuss recent developments in documenting the spread of millet across the Eurasian steppes. We emphasize that, despite a recent proposal that millet consumption in southern Siberia can be attributed to the Early Bronze Age (i.e., the late third to early second millennium BC), at present there are no direct data for southern Siberia indicating the consumption of millet prior to the Late Bronze Age, from the 14th century BC. We also present in full the combined stable isotope and 14C datasets from the Minusinsk Basin to support this conclusion.

Preservatives and consolidants make it difficult or impossible to obtain accurate radiocarbon dates on many organic artefacts from museums or archaeological collections. Discovered in an Irish bog in the 1960s, the Cuillard Bowl is a triangular wooden (Alder - Alnus glutinosa) dish of special interest on account of its unique geometry and style. However, the persistence of preservative (polyethylene glycol, PEG) following conventional pre-treatment methods produced problematic radiocarbon dates. A new ramped pyroxidation (RPO) setup at the 14CHRONO Centre was applied to pretreated material from the Cuillard bowl to investigate if a preservative-free CO2 fraction could be isolated, taking advantage of the release of CO2 from wood cellulose at a lower decomposition temperature than CO2 is released from PEG. Radiocarbon dates on low temperature fractions (280–340 °C) produced statistically identical radiocarbon ages that calibrate from the mid-6th to mid-7th centuries AD, in agreement with stylistic dating of the bowl. The validity of these results is further supported by models of the radiocarbon ages from theoretical thermal decomposition curves of PEG-contaminated wood. Higher temperature fractions (> 350 °C) were statistically different and older due to the removal of CO2 derived from the PEG preservative. RPO and infrared-spectroscopy (FTIR) results on non-pretreated Cuillard bowl material, early medieval alder of known age (dendro-dated), and modern alder were used to identify PEG as the preservative and to provide references for the thermal behaviour of both clean and heavily contaminated wood in the RPO system. This work demonstrates the development of a new technique for radiocarbon dating of organic artefacts that are contaminated by PEG, offering a new avenue for the investigation of museum or archaeological collections previously considered too difficult date.

The Glastonbury Lake Village in Somerset, UK, is made up of 90 mounds comprising 40 roundhouses. Excavations between 1892 and 1907 revealed Iron Age structural and material remains unparalleled in Western Europe. The settlement's exact chronology, however, has remained uncertain. Here, the authors present a programme of radiocarbon and dendrochronological dating and chronological modelling on samples from recent excavations. The results indicate that the site was founded in the early second century cal BC, with the last structures being built just over a century later. This new, robust chronology can be used to date a wide range of associated material culture, and complements chronologies established for other Iron Age sites.

Radiocarbon dating and Bayesian chronological modelling have provided precise new dating for the henge monument of Mount Pleasant in Dorset, excavated in 1970–1. A total of 59 radiocarbon dates are now available for the site and modelling of these has provided a revised sequence for the henge enclosure and its various constituent parts: the timber palisaded enclosure, the Conquer Barrow, and the ditch surrounding Site IV, a concentric timber and stone monument. This suggests that the henge was probably built in the 26th century calbc, shortly followed by the timber palisade and Site IV ditch. These major construction events took place in the late Neolithic over a relatively short timespan, probably lasting 35–125 years. The principal results are discussed for each element of the site, including comparison with similar monument types elsewhere in Britain and Ireland, and wider implications for late Neolithic connections and later activity at the site associated with Beaker pottery are explored.

Connecting calendar ages to radiocarbon (14C) ages, i.e. constructing a calibration curve, requires14C samples that represent, or are closely connected to, atmospheric14C values and that can also be independently dated. In addition to these data, there is information that can serve as independent tests of the calibration curve. For example, information from ice core radionuclide data cannot be directly incorporated into the calibration curve construction as it delivers less direct information on the14C age–calendar age relationship but it can provide tests of the quality of the calibration curve. Furthermore, ice core ages on14C-dated volcanic eruptions provide key information on the agreement of ice core and radiocarbon time scales. Due to their scarcity such data would have little impact if directly incorporated into the calibration curve. However, these serve as important “anchor points” in time for independently testing the calibration curve and/or ice-core time scales. Here we will show that such information largely supports the new IntCal20 calibration record. Furthermore, we discuss how floating tree-ring sequences on ice-core time scales agree with the new calibration curve. For the period around 40,000 years ago we discuss unresolved differences between ice core10Be and14C records that are possibly related to our limited understanding of carbon cycle influences on the atmospheric14C concentration during the last glacial period. Finally, we review the results on the time scale comparison between the Greenland ice-core time scale (GICC05) and IntCal20 that effectively allow a direct comparison of14C-dated records with the Greenland ice core data.

Radiocarbon calibration is necessary to correct for variations in atmospheric radiocarbon over time. The IntCal working group has developed an updated and extended radiocarbon calibration curve, IntCal20, for Northern Hemisphere terrestrial samples from 0 to 55,000 cal yr BP. This paper summarizes the new datasets, changes to existing datasets, and the statistical method used for constructing the new curve. Examples of the effect of the new calibration curve compared to IntCal13 for hypothetical radiocarbon ages are given. For the recent Holocene the effect is minimal, but for older radiocarbon ages the shift in calibrated ages can be up to several hundred years with the potential for multiple calibrated age ranges in periods with higher-resolution data. In addition, the IntCal20 curve is used to recalibrate the radiocarbon ages for the glaciation of the Puget Lowland and to recalculate the advance rate. The ice may have reached its maximum position a few hundred years earlier using the new calibration curve; the calculated advance rate is virtually unchanged from the prior estimate.

Mid-latitude alpine caves preserve a record of past solid precipitation during winter, locally spanning several centuries to millennia. Dating organic macro-remains trapped in ice layers allows the determination of timing and duration of past periods of positive and negative ice mass balance. We present here the largest comparative study of ice cave sites yet published, using Bayesian age-modelling on a database comprising 107 radiocarbon dates, spread over eight caves in the Austrian Alps. We show that periods of positive mass balance coincide with past glacier advances. We find unconformities rich in organic macro-remains dated to the Medieval Climate Anomaly (between 850 and 1200 CE) marking widespread ice retreat. We demonstrate positive ice mass balance at all studied sites for the Little Ice Age, coinciding with the largest glacier advances in the Holocene between 1400 and 1850 CE. At the sites with records spanning over 2000 years, positive mean annual mass balance is also observed during the periods 300 BCE–100 CE and 600-800 CE. These subterranean ice deposits show widespread evidence of accelerated negative mass balances in recent years and their record is under imminent threat of disappearing.

Radiocarbon (14C), as a consequence of its production in the atmosphere and subsequent dispersal through the carbon cycle, is a key tracer for studying the Earth system. Knowledge of past 14C levels improves our understanding of climate processes, the Sun, the geodynamo, and the carbon cycle. Recently updated radiocarbon calibration curves (IntCal20, SHCal20, and Marine20) provide unprecedented accuracy in our estimates of 14C levels back to the limit of the 14C technique (~55,000 years ago). Such improved detail creates new opportunities to probe the Earth and climate system more reliably and at finer scale. We summarize the advances that have underpinned this revised set of radiocarbon calibration curves, survey the broad scientific landscape where additional detail on past 14C provides insight, and identify open challenges for the future.

Authors thank the National Natural Science Foundation of China grants NSFC 41888101 and NSFC 41731174, the 111 program of China (D19002), U.S. NSF Grant 1702816, and the Malcolm H. Wiener Foundation for support for research that contributed to the IntCal20 curve. The work on the Swiss and German YD trees was funded by the German Science foundation and the Swiss National Foundation (grant number: 200021L_157187). The operation in Aix-en-Provence is funded by the EQUIPEX ASTER-CEREGE, the Collège de France and the ANR project CARBOTRYDH (to EB). The work on the correlation of tree ring 14C with ice core 10Be was partially supported by the Swedish Research Council and the Knut and Alice Wallenberg foundation. M. Butzin is supported by the German Federal Ministry of Education and Research (BMBF) through the PalMod project (grant number: 01LP1505B). S. Talamo and M. Friedrich. are funded by the European Research Council under the European Union’s Horizon 2020 Research and Innovation Programme (grant agreement No. 803147-RESOLUTION, awarded to ST). C. Turney would like to acknowledge support of the Australian Research Council (FL100100195 and DP170104665). P. Reimer and W. Austin acknowledge the support of the UKRI Natural Environment Research Council (Grant NE/M004619/1). Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals. Publisher PDF

The Belfast Ramped Pyroxidation/Combustion (RPO/RC) facility was established at the14CHRONO Centre (Queen’s University Belfast). The facility was created to provide targeted analysis of bulk material for refined chronological analysis and carbon source attribution for a range of sample types. Here we report initial RPO results, principally on background material, but also including secondary standards that are routinely analyzed at14CHRONO. A description of our setup, methodology, and background (blank) correction method for the system are provided. The backgrounds (anthracite, spar calcite, Pargas marble) reported by the system are in excess of 35,00014C years BP with a mean age of 39,34514C years BP (1σ = 36,497–43,800 years BP, N=44) with F14C = 0.0075 ± 0.0032. Initial results for standards are also in good agreement with consensus values: TIRI-B pine radiocarbon age = 4482 ± 47 years BP (N=13, consensus = 4508 years BP); IAEA-C6 ANU Sucrose F14C= 1.5036 ± 0.0034 (N=10, consensus F14C = 1.503). These initial tests have allowed problematic issues to be identified and improvements made for future analyses.

The cave bear was a prominent member of the Upper Pleistocene fauna in Eurasia. While breakthroughs were recently achieved with respect to its phylogeny using ancient DNA techniques, it is still challenging to date cave bear fossils beyond the radiocarbon age range. Without an accurate and precise chronological framework, however, key questions regarding the palaeoecology cannot be addressed, such as the extent to which large climate swings during the last glacial affected the habitat and possibly even conditioned the final extinction of this mammal. Key to constraining the age of cave bear fossils older than the lower limit of radiocarbon dating is to date interlayered speleothems using 230Th/U. Here we report new results from one such site in the Eastern European Alps (Schwabenreith Cave), which yielded the highest density of bones of cave bear (Ursus spelaeus eremus). Although dating of the flowstones overlying this fossiliferous succession was partly compromised by diagenetic alteration, the 230Th/U dates indicate that the bear hibernated in this cave after about 113 ka and before about 109 ka. This time interval coincides with the equivalent of Greenland Stadial 25, suggesting possible climate control on the cave bear's habitat and behaviour.

International audience; Evidence for climate variability in the Southern African monsoon region (SAMR) is limited by a spatially and temporally discontinuous palaeoclimatic dataset. We describe a 6680 year long, largely sub-decadal resolution δ 15 N record from a rock hyrax midden from southeastern Africa. The results provide a detailed reconstruction of regional hydroclimates since the beginning of the mid-Holocene. A long-term-albeit subtle-increase in humidity consistent with precessional forcing is observed, but the record is dominated by a strong ~1750-yr cycle, a signal that is shared with other SAMR records. Considered in their regional context, these data suggest that changes coincident with the termination of the African Humid Period at ~5500 cal BP do not express the abrupt transition observed in some records from the northern African tropics. Rather they indicate gradual changes, as observed at peri-equatorial sites. Notably, however, eastern and western subregions of the SAMR experience a rapid phase shift beginning ~5500 cal BP, with initially in-phase hydroclimate anomalies transitioning to the establishment of a strong east-west dipole. This likely reflects a coeval strengthening of the Southeast Atlantic trade winds and decreased atmospheric pressure in southeast Africa, factors associated with increasing (decreasing) austral (boreal) summer insolation. The results highlight the distinct nature of southern African responses across this key period of African climate history.

Model-based projections of ice-sheet thresholds and global sea-level rise are severely constrained by instrumental observations being only decadal to century-long. As we improve our understanding of these processes, projections just a few years old are now considered conservative, raising concerns about our ability to successfully plan for abrupt future change. Past periods of abrupt and extreme warming offer ‘process analogues’ that can provide new insights into the future rate of response of polar ice sheets to warming of the Earth system. The Last Termination (20,000-10,000 years ago or 20-10 ka BP) in the North Atlantic region was characterised by a series of abrupt climatic changes including rapid warming at 14.7 ka BP (the start of the “Bølling”, or GI-1 in the Greenland ice-core isotope stratigraphy) which was accompanied by an Antarctic Cold Reversal (ACR) in the south. Potentially important, during the onset of GI-1, warming persisted in the south for some 256±133 calendar years before the ACR, providing a period of time during which both polar regions experienced increasing temperatures. Sometime around the onset of GI-1 and the ACR, Meltwater Pulse 1A (MWP-1A) formed an abrupt sea level rise of ~15 metres, and was coincident with a period of enhanced iceberg flux in the Southern Ocean. It seems likely the majority of the sea level rise came from the Northern Hemisphere – up to 5-6 metres from the Laurentide Ice Sheet – though the timing remains uncertain. The contribution of Antarctic Ice Sheets (AIS) to global mean sea level (GMSL) rise during MWP-1A range from ‘high-end’ scenarios (>10 m contributing over half of the total GMSL rise), to ‘low-end’ (scenarios with little to no contribution). Here we report the results of a multidisciplinary study, with refined age and Antarctic ice-sheet modelling of the MWP-1A sea-level rise. With the recently released international radiocarbon calibration curve (IntCal20), our Bayesian age modelling of terrestrial ages from flooded mangrove swamps suggests global sea level rose across a mean age range of 14.58 ka BP to 14.42 ka BP, with a mean rate of sea-level rise of 0.94 metres per decade (14.97 metres over 160 years). Because the calibrated age range at 95% confidence overlaps in this age model, it is possible the 15 metre rise during MWP1A could have taken place essentially instantaneously. Even the most conservative age modelling we have undertaken indicates an extraordinary rapid rate of sea-level rise; two orders of magnitude larger than the mean rate of global sea level rise since 1993 (0.03±0.003 metres per decade). Our ice-sheet modelling suggests a substantial and rapid loss of Antarctic ice mass (mostly from the Weddell Sea Embayment and the Antarctic Peninsula), synchronous with warming and ice loss in the North Atlantic. The drivers and mechanisms of the observed near-synchronous interhemispheric changes will be discussed, with implications for the future.

Sequestration of organic carbon in aquatic sediments can depend on its source and potential lability. Studies have shown that bulk lake and marine sediment comprises carbon of different origin but its source has been difficult to attribute. A new Ramped Pyroxidation/Combustion (RPO) system in the 14CHRONO Centre has been established. RPO is a technique that incrementally heats a sample, and allows for collection of the CO2 produced for radiocarbon analyses. The results show its utility in partitioning carbon sources in lake sediment (Rostherne Mere, UK, Santa María del Orolake, Mexico), and arctic marine sediment (Chukchi Sea and Beaufort Shelf). RPO and 2-stepped combustion1. 14C indicated multiple carbon sources in Rostherne Mere sediment, some of which could be attributed to the construction of a sewage treatment works (STW) on the lake shore, and subsequently inputs from this STW. RPO identified 3 carbon fractions in Mexican Lake sediment, which provided a more accurate chronology, partitioning the contemporaneous sediment date from offsets induced from volcanic activity in the area. Results from Arctic marine sediment demonstrated inputs of carbon from ancient permafrost, providing a means to refine the chronologies and a basis for future research linked with carbon loss from thawing permafrost.1Keaveney et al. 2020. Journal of Palaeolimnology 64 347-363

Highlights: • NW Pacific ice-rafted debris found further south than previously thought. • Largest iceberg events were comparable in magnitude to N Atlantic Heinrich Events. • Iceberg flux to ODP Site 1207 was episodic throughout the late Quaternary. • Kamchatka-Koryak bergs frequently reached south of the N Pacific Subarctic Front. • Ice-rafting and climate contrast sharply between the last two glacial periods. Abstract: The ice-rafted-debris (IRD) record of the open Northwest Pacific points towards the existence of substantial glacial ice on the Northeast Siberian coast during the late Quaternary. However, the scale and timing of glaciation and de-glaciation remains controversial due to the dearth of both onshore and offshore records. Existing IRD data suggests at least one event of dynamic and abrupt change during mid-late Marine Isotope Stage (MIS 3) which mimics the massive collapse of the Laurentide ice sheet during Heinrich Events. It is uncertain whether other events of this magnitude occurred during the late Quaternary. Here we present a ∼160,000 yr IRD series, planktic foraminiferal counts and an age model, derived from a benthic O curve, radiocarbon dates and tephrochronology, from core ODP 1207A (37.79°N, 162.75°E), revealing the presence of low but episodic flux of IRD. We conclude that glacial Northwest Pacific icebergs spread further south than previously thought, with icebergs emanating from Northeast Siberia being transported to the transition region between the subpolar and subtropical waters, south of the subarctic front during at least the Quaternary's last two glacial periods. The episodic nature of the 1207A IRD record during the last glacial, combined with coupled climate-iceberg modelling, suggests occasional times of much enhanced ice flux from the Kamchatka-Koryak coast, with other potential sources on the Sea of Okhotsk coast. These findings support the hypothesis of a variable but extensive ice mass during the last glacial over Northeast Siberia, particularly early in the last glacial period, behaving independently of North American and Eurasian ice masses. In strong contrast, IRD was absent during much of the penultimate glacial Marine Isotope Stage (MIS) 6 suggesting the possibility of very different Northeast Siberian ice coverage between the last two glacial periods.

We explored the roles of phytoplankton production, carbon source, and human activity on carbon accumulation in a eutrophic lake (Rostherne Mere, UK) to understand how changes in nutrient loading, algal community structure and catchment management can influence carbon sequestration in lake sediments. Water samples (dissolved inorganic, organic and particulate carbon) were analysed to investigate contemporary carbon sources. Multiple variables in a 55-cm sediment core, which represents the last ~ 90 years of accumulation, were studied to determine historical production rates of algal communities and carbon sources. Fluctuations in net primary production, inferred from sedimentary diatom abundance and high-performance liquid chromatography (HPLC) pigment methods, were linked to nutrient input from sewage treatment works (STW) in the catchment. Stepped combustion radiocarbon (SCR) measurements established that lake sediment contains between 11% (~ 1929 CE) and 69% (~ 1978 CE) recalcitrant carbon, with changes in carbon character coinciding with peaks in accumulation rate and linked to STW inputs. Catchment disturbance was identified by radiocarbon analysis, and included STW construction in the 1930s, determined using SCR analysis, and recent nearby highway construction, determined by measurements on dissolved organic carbon from the lake and outflow river. The quantity of autochthonous carbon buried was related to diatom biovolume accumulation rate (DBAR) and decreased when diatom accumulation rate and valve size declined, despite an overall increase in net carbon production. HPLC pigment analysis indicated that changes in total C deposition and diatom accumulation were related to proliferation of non-siliceous algae. HPLC results also indicated that dominance of recalcitrant carbon in sediment organic carbon was likely caused by increased deposition rather than preservation factors. The total algal accumulation rate controlled the sediment organic carbon accumulation rate, whereas DBAR was correlated to the proportion of each carbon source buried.

Archaeological excavation of a natural boulder chamber on the upper slopes of Bengorm Mountain, County Mayo, in the north-west of Ireland revealed evidence for complex Neolithic funerary rituals spanning several centuries. With virtually no subsequent evidence of animal or human disturbance, the site presents an exceptional insight into well-preserved engagements with the dead at a remote mountain location where themes of secrecy, continuity and ritual grammar are highlighted. The chamber was used for processing individuals of all ages but there is a tentative suggestion that the space was reserved predominantly for males. Ancient genomic analysis reveals kinship between at least two adult males, both of whom were almost certainly intermediate to dark skinned, with brown eyes and dark brown or black hair. Both individuals were also lactose intolerant.

The new radiocarbon calibration curve (IntCal20) allows us to calculate the gradient of the relationship between 14 C age and calendar age over the past 55 millennia before the present (55 ka BP). The new gradient curve exhibits a prolonged and prominent maximum between 48 and 40 ka BP during which the radiocarbon clock runs almost twice as fast as it should. This radiocarbon time dilation is due to the increase in the atmospheric 14 C/ 12 C ratio caused by the 14 C production rise linked to the transition into the Laschamp geomagnetic excursion centered around 41 ka BP. The major maximum in the gradient from 48 to 40 ka BP is a new feature of the IntCal20 calibration curve, with far-reaching impacts for scientific communities, such as prehistory and paleoclimatology, relying on accurate ages in this time range. To illustrate, we consider the duration of the overlap between Neanderthals and Homo sapiens in Eurasia.

T.J. Heaton is supported by a Leverhulme Trust Fellowship RF-2019-140\9, “Improving the Measurement of Time Using Radiocarbon”. M Butzin is supported by the German Federal Ministry of Education and Research (BMBF), as Research for Sustainability initiative (FONA); www.fona.de through the PalMod project (grant numbers: 01LP1505B, 01LP1919A). E. Bard is supported by EQUIPEX ASTER-CEREGE and ANR CARBOTRYDH. Meetings of the IntCal Marine Focus group have been supported by Collège de France. The concentration of radiocarbon (14C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their 14C in the marine environment therefore need a marine-specific calibration curve and cannot be calibrated directly against the atmospheric-based IntCal20 curve. This paper presents Marine20, an update to the internationally agreed marine radiocarbon age calibration curve that provides a non-polar global-average marine record of radiocarbon from 0–55 cal kBP and serves as a baseline for regional oceanic variation. Marine20 is intended for calibration of marine radiocarbon samples from non-polar regions; it is not suitable for calibration in polar regions where variability in sea ice extent, ocean upwelling and air-sea gas exchange may have caused larger changes to concentrations of marine radiocarbon. The Marine20 curve is based upon 500 simulations with an ocean/atmosphere/biosphere box-model of the global carbon cycle that has been forced by posterior realizations of our Northern Hemispheric atmospheric IntCal20 14C curve and reconstructed changes in CO2 obtained from ice core data. These forcings enable us to incorporate carbon cycle dynamics and temporal changes in the atmospheric 14C level. The box-model simulations of the global-average marine radiocarbon reservoir age are similar to those of a more complex three-dimensional ocean general circulation model. However, simplicity and speed of the box model allow us to use a Monte Carlo approach to rigorously propagate the uncertainty in both the historic concentration of atmospheric 14C and other key parameters of the carbon cycle through to our final Marine20 calibration curve. This robust propagation of uncertainty is fundamental to providing reliable precision for the radiocarbon age calibration of marine based samples. We make a first step towards deconvolving the contributions of different processes to the total uncertainty; discuss the main differences of Marine20 from the previous age calibration curve Marine13; and identify the limitations of our approach together with key areas for further work. The updated values for ΔR, the regional marine radiocarbon reservoir age corrections required to calibrate against Marine20, can be found at the data base http://calib.org/marine/. Publisher PDF

To create a reliable radiocarbon calibration curve, one needs not only high-quality data but also a robust statistical methodology. The unique aspects of much of the calibration data provide considerable modeling challenges and require a made-to-measure approach to curve construction that accurately represents and adapts to these individualities, bringing the data together into a single curve. For IntCal20, the statistical methodology has undergone a complete redesign, from the random walk used in IntCal04, IntCal09 and IntCal13, to an approach based upon Bayesian splines with errors-in-variables. The new spline approach is still fitted using Markov Chain Monte Carlo (MCMC) but offers considerable advantages over the previous random walk, including faster and more reliable curve construction together with greatly increased flexibility and detail in modeling choices. This paper describes the new methodology together with the tailored modifications required to integrate the various datasets. For an end-user, the key changes include the recognition and estimation of potential over-dispersion in14C determinations, and its consequences on calibration which we address through the provision of predictive intervals on the curve; improvements to the modeling of rapid14C excursions and reservoir ages/dead carbon fractions; and modifications made to, hopefully, ensure better mixing of the MCMC which consequently increase confidence in the estimated curve.

This paper presents the results of stable isotope analysis of the Saka period population of Central Kazakhstan. The analysed materials originate from 37 sites of the Tasmola Culture which is presently dated to the 8th - 5th c. BC. The sample include 31 humans from 31 burials and 6 animals from three settlements and three burials. Human isotopic results are widely scattered both in δ13C, and in δ15N ratios from the cemeteries of Koitas, Taldy-2, Akbeit and Karashoky. The obtained data suggests the presence of millet in Central Kazakhstan in the beginning of the Early Iron Age, either as agricultural crop or imported product. The findings of a small quantity of millet and barley grains in the cultural layer of one of the Tasmola Culture settlements supports this hypothesis. These findings represent the first phase of the research. A more representative series of samples, including faunal, is needed for a more comprehensive investigation of the topic.

This paper presents the results of a study using strontium, oxygen and carbon isotopes, strontium concentrations, infrared analyses and radiocarbon dating to investigate human mobility and landscape use as seen in individuals from the Neolithic court tomb of Parknabinnia, Co. Clare, Ireland. Taking advantage of the recent demonstration that it is possible to obtain reliable in vivo strontium isotope signals from calcined bone, we compare measurements on cremated bone (n = 4) and uncremated tooth enamel (n = 4). The results suggest that two out of four uncremated enamel samples can be considered ‘local’ while the other two, and all four cremated bone samples, represent ‘non-local’ individuals. New radiocarbon dates obtained on two of the cremated bone fragments place them in the Chalcolithic/Early Bronze Age, contrasting with the Neolithic dates previously obtained on the uncremated remains, demonstrating re-use of the monument. Assuming that our small sample is representative, it seems that the court tomb was used for burial by both ‘locals’ and ‘non-locals’ during the Neolithic and predominantly by ‘non-locals’ in the Chalcolithic/Early Bronze Age. This stands in contrast to the nearby Early Neolithic portal tomb of Poulnabrone where only one individual (of 17 analysed) appears to be an ‘outsider’. Our results suggest that, even within a small region, mobility and landscape use may have differed significantly within the Neolithic and also between the Neolithic and the Chalcolithic/Early Bronze Age., SCOPUS: ar.j, info:eu-repo/semantics/published

Mid-latitude, cave-hosted temperate ice is increasingly scrutinised for its palaeoclimatic potential. Findings of dendrochronologically dated wood trunks and radiometrically dated woody macrofossils demonstrate that underground ice accumulations records may locally span several millenia. The cave geometries conducive to underground firn accumulation were additionally shown to favour the preservation of a winter signal, making cave-hosted ice an attractive and complementary archive to existing and largely summer-biased proxy records. Proxy derivation from these ice accumulations first requires the establishment of firn accumulation/ablation chronologies from stratigraphic mapping and radiometric dating of organic inclusions. Decadal to centennial trends in accumulation/ablation recorded by the ice stratigraphy thus provide insight in past variations of solid precipitation .Preliminary results from several well-dated ice caves of the Northern Calcareous Alps in Austria suggest local preservation of ice since ca. 3600-3300 BC. Inclusion-rich unconformities in the ice stratigraphy from these alpine caves mark short breaks in firn accumulation between 250 BC and 250 AD and longer hiatuses during Late Antiquity and the 8th and 9th century AD. The majority of dated ice sequences testify the onset of rapid ice accumulation from the 11th and 12th century AD onwards and build up throughout the 'Litte Ice Age'.

Paleoclimate records from the North Atlantic show some of the most iconic signals of abrupt climate change during the ice ages. Here we use radiocarbon as a tracer of ocean circulation and air-sea gas exchange to investigate potential mechanisms for the abrupt climate changes seen in the North Atlantic over the last deglaciation. We have created a stack of North Atlantic surface radiocarbon reservoir ages over the past 20,000 years, using new synchronized age models from thirteen sediment cores refined with thorium normalization between tie-points. This stack shows consistent and large reservoir age increases of more than 1000 years from the LGM into HS1, dropping abruptly back to approximately modern reservoir ages before the onset of the Bolling-Allerod. We use the intermediate complexity earth system model cGENIE to investigate the potential drivers of these reservoir age changes. We find that sea ice, circulation and CO2 all play important roles in setting the reservoir age. We use these coherently dated records to revisit the sequence and timing of climatic events during HS1 and the last deglaciation, and show that Laurentide Heinrich Events are a response to stadial conditions, rather than their root cause.

The construction of the new IntCal20 calibration curve was undertaken using a number of new statistical approaches (Heaton et al. 2020), when compared to previous versions. This was partly due to the nature of some of the new datasets; partly to improve the robustness of the curve; and partly to address particular aspects of radiocarbon within the Earth System such as reservoir effects, incorporation of geological carbon in speleothems, and the uncertainties associated with different timescales. Here the main approaches taken are summarised with a perspective on their strengths and potential weaknesses.In particular, the high-resolution extensions to the Hulu speleothem radiocarbon record (Cheng et al. 2018) allow it to be used to anchor the chronology for other key records (Suigetsu, Cariaco, and the Pakistan and Iberian Margins), providing a coherence in the timescale not possible before. Further, for the first time, we incorporate time varying marine reservoir ages, constrained by the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM)(Butzin et al. 2020). In addition, work on the relationship to the Greenland ice core timescales (Adolphi et al. 2018) enables us to make direct comparison between radiocarbon dated records and the ice core timescale and here we report on tools to assist with this.Along with the update to the calibration curve itself, the associated tools for calibration, age-depth modelling and Bayesian modelling have also been updated to make best use of the new resolution and characteristics of the curve. Here we summarise updates to Bacon, Calib and OxCal.Heaton, TJ. et al (2020) The IntCal20 approach to radiocarbon calibration curve construction: A new methodology using Bayesian splines and errors-in-variables Radiocarbon: in review.Cheng, H. et al. (2018) Atmospheric 14C/12C changes during the last glacial period from Hulu Cave. Science, 362(6420), pp.1293-1297. doi:10.1126/science.aau0747Adolphi, F. et al. (2018) Connecting the Greenland ice-core and U/Th timescales via cosmogenic radionuclides: Testing the synchronicity of Dansgaard-Oeschger events. Climate of the Past, 14, pp.1755-1781. doi:10.5194/cp-2018-85Butzin, M. et al. (2020) A short note on marine reservoir age simulations used in IntCal20. Radiocarbon: in press.

In the Alpine foreland and the Vienna Basin loess-paleosol sequences (LPS) are common. Some of the most famous LPS sites in the circum-Alpine area include Stratzing, Göttweig, Willendorf, Krems-Wachtberg, and Stillfried, which cluster in a relatively small area along the Danube river in Lower Austria. LPS provide detailed insights into climate-driven, terrestrial palaeoenvironmental changes that can be placed into a robust chronological framework, because LPS are amenable to a range of dating techniques. Here, we present a well-dated 13.6 m-thick mammoth-bearing sediment succession characterised by low-energy aquatic deposits, sheet-flow deposits and sandy loess from re-deposited Miocene sediments, i.e. a depositional environment that contrasts to the classical LPS sites. This new site is situated 1.6 km NNE of Bullendorf in Lower Austria, where Pleistocene sediment successions with a robust chronology are rare. Our multidisciplinary approach is based on optically stimulated luminescence and 14C dating, and includes mammal faunal investigations and stable isotope analyses of molluscs. OSL and 14C dating suggest deposition of the sediment sequence immediately before and briefly after the Last Glacial Maximum. The mollusc assemblages and the mammal fauna are representative of a cold climate, characteristic of a tundra steppe environment. Stratigraphic changes in δ18O of two mollusc species (Pupilla muscorum and Succinella oblonga) suggest an alternating dry-cold and humid-cold climate. Oxygen isotope data of freshwater gastropod shells suggest a drastic decrease in the mean growing season temperature compared to today, while the carbon isotope composition is indicative of a C3 vegetation.

How climate and ecology affect key cultural transformations remains debated in the context of long-term socio-cultural development because of spatially and temporally disjunct climate and archaeological records. The introduction of agriculture triggered a major population increase across Europe. However, in Southern Scandinavia it was preceded by ~500 years of sustained population growth. Here we show that this growth was driven by long-term enhanced marine production conditioned by the Holocene Thermal Maximum, a time of elevated temperature, sea level and salinity across coastal waters. We identify two periods of increased marine production across trophic levels (P1 7600–7100 and P2 6400–5900 cal. yr BP) that coincide with markedly increased mollusc collection and accumulation of shell middens, indicating greater marine resource availability. Between ~7600–5900 BP, intense exploitation of a warmer, more productive marine environment by Mesolithic hunter-gatherers drove cultural development, including maritime technological innovation, and from ca. 6400–5900 BP, underpinned a ~four-fold human population growth., How the development of human societies is influenced through their ecological environment and climatic conditions has been the subject of intensive debate. Here, the authors present multi-proxy data from southern Scandinavia which suggests that pre-agricultural population growth there was likely influenced by enhanced marine production.

Excavations on the south-eastern slopes of King Barrow Ridge, 1.5 km east of Stonehenge, revealed five pits, a grave and other features of Middle Neolithic date. Analysis of the pit assemblages and the partial inhumation interred in the grave has provided insights into lifeways in this landscape in the late fourth millennium cal BC. Evidence suggests that the area was visited by a pastoralist, mobile community on a semi-regular basis for a significant period, in late autumn or winter. Selected remnants of craft-working and consumption were deposited in pits, before deliberate infilling. These depositions repeatedly memorialised activity on the hillside at a time of contemporary activity elsewhere on King Barrow Ridge and at the future site of Stonehenge. Middle Neolithic pits are present in significant numbers across King Barrow Ridge, and alongside pits in the Durrington area, form one of the densest concentrations of such activity in the region. Long distance mobility is suggested by the possible Irish origins of the inhumation, the first Middle Neolithic individual excavated in the environs of Stonehenge. Whilst of significance for understanding the Middle Neolithic in the WHS and the region, this research also hints at the roots of Late Neolithic monumentalisation of this landscape.

We conducted inter-laboratory AMS 14C dating of bones of the Miesenheim IV elk (Rhineland, Germany), buried under Laacher See tephra dated to ca. 11,060 BP (13,000 cal BP). The weighted mean of A laboratory inter-comparison of AMS 14C dating of bones of the Miesenheim IV elk (Rhineland, Germany) and its implications for the date of the Laacher See eruptionthe new dates, which range from 10,920 to 11,270 BP, is 11,092 ± 19 BP. The consistent results from five AMS laboratories are important in two respects. First, they demonstrate that collagen processed by traditional methods can yield accurate ages; the newly obtained 14C dates are in accord with previous hydroxyproline 14C value generated at the Oxford AMS laboratory within the first round of inter-comparison (Fiedel et al., 2013). The results of the first inter-comparison are clearly flawed, except for hydroxyproline 14C date (see Fiedel et al., 2013), and must be affected by the waxy/dark, presumably humic/organic-based contaminant. Second, they provide a new suite of radiocarbon dates for the Laacher See volcanic eruption, a crucial anchor point for Late Glacial chronology in central Europe.

Consumption of marine protein in humans and animals can result in an apparent older radiocarbon (14C) age due to reservoir offsets. In order to correct for this, an estimate of the marine protein intake should be used to correct the 14C age for reservoir offsets, which is ordinarily done using δ13C or δ15N values. However, these two isotopic proxies can be influenced by a number of factors which can hamper estimation of the correct marine protein intake. A small dataset of 12 samples from the Limfjord, Denmark, ranging in age from Mesolithic to Viking Age, was used to test the use of δ2H values to quantify marine protein intake and determine the reservoir corrections. Each of the three stable isotopic values (δ2H, δ13C, δ15N) was used to estimate the percent marine protein intake, which produced three different calibrated 14C ages. The calculated percent marine protein intake differed between the use of the stable isotopic ratios with a maximum difference of 42.1% between the use of δ15N and δ13C, 23.8% between δ2H and δ13C, and 46.2% between δ2H and δ15N. In some cases the calculated percent marine protein intake changed the sample’s archaeological period, although there was generally still overlap in the archaeological periods for samples used in this study.

Osteobiographies of four individuals whose skeletal remains were recovered in 2015–16 from the Stonehenge World Heritage Site are constructed, drawing upon evidence from funerary taphonomy, radiocarbon dating, osteological study, stable isotope analyses, and microscopic and biomolecular analyses of dental calculus. The burials comprise an adult from the Middle Neolithic period, immediately prior to the building of Stonehenge, and two adults and a perinatal infant dating from the Middle Bronze Age, shortly after the monument ceased to be structurally modified. The two Middle Bronze Age adults were closely contemporary, but differed from one another in ancestry, appearance and geographic origin (key components of ethnicity). They were nevertheless buried in very similar ways. This suggests that aspects they held in common (osteological analysis suggests perhaps a highly mobile lifestyle) were more important in determining the manner of deposition of their bodies than any differences between them in ethnicity. One of these individuals probably came from outside Britain, as perhaps did the Middle Neolithic adult. This would be consistent with the idea that the Stonehenge landscape had begun to draw people to it from beyond Britain before Stonehenge was constructed and that it continued to do so after structural modification to the monument had ceased.

Anthropogenic pressures on the marine environment have escalated and shellfish habitats have declined around the world. Recently, Marine Protected Areas (MPAs) have rapidly increased in number and extent, but in Europe as elsewhere, management baselines rarely account for historical conditions.In the present study, the Dornoch Firth protected area (NE Scotland) was investigated as well as three adjacent inlets and 50 km of open coastline. The area has low levels of industrial development, is sparsely populated and conservation features were previously considered “Favourable”. The aim of the present study was to investigate the historical presence of native oyster (Ostrea edulis) beds, a habitat that is now rare and of conservation importance throughout Atlantic Europe.Centred on the protected area, but also gathering broader information from East Scotland, an interdisciplinary review was made of archaeological records, navigational charts, historical maps, museum collections, land-use records, fisheries records, public online databases and naturalists’ records. Intertidal and subtidal surveys were also conducted and sample oyster shells were radiocarbon dated.The present study shows that O. edulis occurred in the inlets and open coast areas of NE Scotland, and specifically in the protected area: Probably since the end of the last glaciation to the late 1800s when they were likely fished to extinction. Habitat restoration in protected areas is an emerging global theme. However, marine habitat restoration is highly unusual and European oyster restoration is presently confined to remnant populations with a clear history of exploitation or dwindling associated fisheries. An interdisciplinary review of baselines will probably show scope for O. edulis restoration in many other European MPAs.

The application of tattoos to the human body has enjoyed a long and diverse history in many ancient cultures. At present, the oldest surviving examples are the mainly geometric tattoos on the individual known as Otzi, dating to the late 4th millennium BCE, whose skin was preserved by the ice of the Tyrolean Alps. In the Egyptian Nile valley, the arid climate has also promoted extensive soft tissue preservation. Here we report on the tattoos found during the examination of two of the best preserved naturally mummified bodies from Egypt's Predynastic (c. 4000-3100 BCE) period, making them the earliest extant examples from the Nile Valley. Figural tattoos that mirror motifs found in Predynastic art were observed on the right arm of one male and the right arm and shoulder of one female, demonstrating conclusively that tattooing was practiced in prehistoric Egypt. These findings overturn the circumstantial evidence of the artistic record that previously suggested only females were tattooed for fertility or even erotic reasons. Radiocarbon testing and datable iconographic parallels for the motifs indicate that these tattooed individuals are nearly contemporaneous with the Iceman, positioning them amongst the bearers of some of the oldest preserved tattoos in the world. At over five thousand years of age, they push back the evidence for tattooing in Africa by a millennium and provide new insights into the range of potential uses of tattoos in pre-literate societies by both sexes, revealing new contexts for exploring the visual language of prehistoric times.

Despite the rich archaeological heritage present in the Limfjord region in Denmark, few palaeodietary studies using human and animal bone material from this area currently exist. This paper aims to investigate the palaeodiet as well as animal husbandry strategies in this region during prehistoric times, from the Mesolithic to the Viking Age using stable isotope analysis. New stable isotope results from almost 300 human and animal bones are presented here, as well as their comparison with previously published data. Higher δ15N values in sheep/goats than cattle suggest that cattle were more confined while the sheep/goats were allowed to roam and possibly consume salt-marsh grass. The stable isotope results reveal a rise in δ15N ratios in human individuals from the Iron Age, which is most likely related to the combined effects of fertilisation practices and aquatic protein consumption. Additionally, evidence for marine exploitation in the form of shell middens and fish remains can be linked to periods characterised by climatic deterioration.

We report radiocarbon (14C) dates on bone samples of Ursus ladinicus, a small cave bear species well adapted to a life in the mountains, whose remains were found in Conturines Cave. Located at 2775 m asl in the Dolomites of northern Italy, this cave is by far the highest known cave bear site worldwide. Eleven 14C dates obtained by the Belfast and Oxford laboratories on samples showing good collagen preservation yielded consistent ages in excess of 46–50 ka BP. These results show that contrary to the previously held view these cave bear remains are older than Marine Isotope Stage 3, and likely date from a warm climate period with a high treeline, possibly the Last Interglacial.