AMS Radiocarbon Measurements Research Articles

Testing and assessment of high-precision and high-accuracy AMS-radiocarbon measurements at Nanjing University, China

AbstractIn 2018, an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) accelerator mass spectrometer (AMS) was installed at the Laboratory of AMS Dating and the Environment, Nanjing University (NJU-AMS Laboratory), China. The NJU-AMS Laboratory is largely devoted to research on radiocarbon dating and 14C analysis in fields of earth, environmental and archaeological sciences. The laboratory has successfully employed various pretreatment methods, including routine pretreatment of tree rings, buried wood and subfossil wood, seeds, charcoal, pollen concentrates, organic matter, and shells. In this study, operational status of the NJU-AMS is presented, and results of radiocarbon measurements made on different sample types are reported. Measurements on international standards, references of known age, and blank samples demonstrate that the NJU-AMS runs stably and has good reproducibility on measurement of single samples. The facility is capable of measuring 14C in samples with the precision and accuracy that meet the requirements for investigating annual 14C changes, history-prehistory age dating, and Late Quaternary stratigraphic chronology research.

Are crucible steel ingots isotopically homogenous? AMS radiocarbon measurements on ingots from Telangana, India

Radiocarbon analysis is increasingly used to directly date archaeological and historical metal objects, ranging from low-carbon bloomery iron to steel and cast iron. However, little is known about the isotopic homogeneity of iron-carbon alloys, particularly relating to the formation of primary cementite during crystallisation. Here, we present 14C measurements for five crucible steel ingots and one crucible steel object from Telangana in south-central India. Two of the ingots were analysed twice. The results show a very wide scatter of 14C dates, far exceeding the expected age range for this assemblage. The repeat analysis of one of the ingots gave also widely different results, indicating a fundamental problem with the 14C analysis of crucible steel. We discuss the various factors that could have influenced the measured isotopic values, including variability in raw material, sampling contamination, and fractionation during the cleaning of the metal in hot acid leading to excessive sample mass losses prior to the extraction of carbon from the metal. We argue that mass-dependant fractionation of the different carbon isotopes between austenite and cementite during solidification of the ingot, and subsequent selective dissolution of one metal phase over the other, led to a distortion of the 14C signature to seemingly older ages. We recommend further research to explore the compound-specific isotopic signature of high-carbon iron alloys and the effect of selective corrosion on such material, to reduce potential errors in 14C dating of steel and cast iron.

Evolution of the inter-reef Halimeda carbonate factory in response to Holocene sea-level and environmental change in the Great Barrier Reef

The inter-reef Halimeda bioherms of the northern Great Barrier Reef (GBR) have accumulated up to 25 m of positive relief and up to four times greater volume of calcium carbonate sediment than the nearby coral reefs during the Holocene. Covering >6000 km2, the Halimeda bioherms represent a significant contribution to the development of the northeast Australian continental shelf geomorphology, neritic carbonate factory, and sedimentary archive of post-glacial environmental changes. However, the geochronological record of initiation and development of the Halimeda bioherm carbonate factory was poorly constrained and based on very few datapoints. A comprehensive age dataset is presented, comprising sixty-three new AMS radiocarbon measurements of Halimeda and foraminifera grains, mollusc shells and bulk soil from twelve inter-reef sediment cores, and ten previously published Halimeda ages. Facies transitions and environmental changes are recorded from lithological and palynological analyses spanning Last Interglacial Halimeda deposits, Last Glacial Maximum terrestrial palaeosols, transgressive mangrove vegetated shorelines, and the turn-on of the Halimeda bioherm carbonate factory. Mangrove pollen and coral records from the study area provide additional spatial, temporal and environmental context.Halimeda had established by 11.1 cal kyr BP, just 450 years after transgressive shelf inundation and approximately 1000 years earlier than previous inferred estimates. The outer-shelf carbonate factory was initially dominated by benthic foraminifera, then Halimeda was productive for at least 2100 years prior to the turn-on of Holocene coral reefs in the study area at 8.9 cal kyr BP from Boulder Reef (15.4°S, 145.4°E). Inter-reef Halimeda bioherms play a major role in carbon and nutrient cycling and potentially preserve a near-continuous geochemical record of northeast Australian Holocene oceanographic and climatic changes, filling spatial and temporal gaps not covered by coral and other marine sediment proxies.

On the Earliest Use of Plate-Formed Cheekpieces and the Emergence of Horse Riding (Based on Finds from the Novoilyinovskiy II Cemetery in Northern Kazakhstan)

This study addresses the description, use-wear analysis, and date of three plate-formed cheekpieces from kurgan 5 at Novoilyinovskiy II, Kazakhstan. They were found in the same context with two sacrificed horses (a stallion and a mare), placed on the bottom of a ritual pit in the “flying gallop” posture. The emergence of horse riding, marking a new type of mobility and warfare, has been traditionally dated to ca 900 BC. However, cheekpieces suggest that this process spanned the entire 2nd millennium BC. They testify to the evolution of horsemanship and the search for the most efficient means of controlling draft and riding horses. Results of the use-wear analysis suggest that all three specimens likely belonged to riding horses’ harnesses. Two AMS radiocarbon measurements referring to kurgan 5 suggest that these cheekpieces are among the earliest used for controlling riding rather than draft horses, implying that horse riding emerged on the Eurasian steppes as early as the beginning of the 2nd millennium BC.

The absolute chronology of the Late Bronze Age settlements Kammenyi Ambar and Ust’ye I in the Southern Trans-Urals and its Bayesian analysis

In this paper, we examine the series of AMS radiocarbon measurements (N = 52) obtained from the Late Bronze Age settlements of Kamennyi Ambar and Usty’e I in the Southern Trans-Urals, Russia. The exploratory data analysis applied to uncalibrated dates allows for the batches and outliers isolation. Furthermore, based on the facts of stratigraphy and application of the Bayesian statistics, we reconstruct the chronology, estimate spans of habitation, and discuss issues of the existing samples. As the first step of the analysis, we consider archaeo-logical contexts of the measurements and statistically identify apparent outliers. Despite the small sample size, the dataset from Ust’ye I obtained in the way that allows to date stratigraphically isolated construction/utilization episodes and thus are highly reliable. At least five measurements from Kamennyi Ambar date the natural events before the settlement construction and serve as upper limits in models. On the second stage of the analysis, the Bayesian models of the sites’ chronology constructed with OxCal 4.3. For Ust’ye I, we designed a three-phase model that allows to date two early habitational phases during which the walls and ditches were built around the settlement. The third phase defines the lower limit of the previous period, as this phase consists of a single radio-carbon measurement. The model suggests the existence of the gap between the two earliest stages, associated with the Sintashta and Petrovka ceramic types. While the sample size is small, this hypothesis agrees well with the site’s stratigraphy, as the settlement was re-modeled entirely at least once. We designed two models for Kamennyi Ambar. The first model includes all available data and consists of three phases: 1) natural events be-fore the settlement construction; 2) the early «walled» phase; 3) the late «unwalled» phase. The second model incorporates data on the wells’ stratigraphy and uses only measurements from the wells. The models almost the same for the early habitational phase, but the modeled chronology of the late phase differs drastically, as the wells-based model condenses the phase and pushes it earlier. Further, the models suggest that Kamennyi Ambar existed only for about 50 years, and Usty’e I for nearly 100 years. The habitational phases within the same peri-ods are partially desynchronized, and possible gaps in the habitation suggested by the models. One possible explanation of the short-term habitation spans and differences is that people needed to resettle regularly as re-source depletion made the areas inhospitable for the communities of the livestock breeders.

К вопросу о времени начала использования желобчатых псалиев и возникновения всадничества (по материалам могильника Новоильиновский II в Северном Казахстане)

This study addresses the description, use-wear analysis, and date of three plate-formed cheekpieces from kurgan 5 at Novoilyinovskiy II, Kazakhstan. They were found in the same context with two sacrificed horses (a stallion and a mare), placed on the bottom of a ritual pit in the “flying gallop” posture. The emergence of horse riding, marking a new type of mobility and warfare, has been traditionally dated to ca 900 BC. However, cheekpieces suggest that this process spanned the entire 2nd millennium BC. They testify to the evolution of horsemanship and the search for the most efficient means of controlling draft and riding horses. Results of the use-wear analysis suggest that all three specimens likely belonged to riding horses’ harnesses. Two AMS radiocarbon measurements referring to kurgan 5 suggest that these cheekpieces are among the earliest used for controlling riding rather than draft horses, implying that horse riding emerged on the Eurasian steppes as early as the beginning of the 2nd millennium BC.

AMS radiocarbon measurement with high accuracy

A project of 14C trace on deep water in South China Sea requires an accuracy of AMS radiocarbon measurement better than 2.5‰, which is higher than the accuracy for routine measurements of the NEC compact AMS system at Peking University. A series of modifications have enhanced the stability of the AMS system, minimizing fractionation effects and improving the accuracy and quality control of measurements. The ripple of terminal voltage has been reduced from 100 V to less than 50 V. The variation of beam currents from different samples is within 20% and a special tool is designed for proper installation of sample wheels. Measurements on standards and secondary samples demonstrate an improvement in accuracy to <2.5‰.

A novel tertiary prep-HPLC method for the isolation of single amino acids for AMS-radiocarbon measurement.

AMS-radiocarbon measurements of amino acids can potentially provide more reliable radiocarbon dates than bulk collagen analysis. Nonetheless, the applicability of such an approach is often limited by the low-throughput of existing isolation methods and difficulties in determining the contamination introduced during the separation process. A novel tertiary prep-HPLC amino acid isolation method was developed that relies on the combustion of eluted material without requiring any additional chemical steps. Amino acid separation was carried out using a gradient mix of pure water and phosphoric acid with an acetonitrile step in-between runs to remove hydrophobic molecules from the separation column. The amount of contaminant carbon and its 14C content were determined from two-point measurements of collagen samples of known 14C content. The amount of foreign carbon due to the isolation process was estimated at 4±1μg and its 14C content was 0.43±0.01 F14C. Radiocarbon values corrected for carbon contamination have only a minor increase in uncertainties. For Holocene samples, this corresponds to an added uncertainty typically smaller than 10 14Cyears. The developed method can be added to routine AMS measurements without implying significant operational changes and offers a level of measurement uncertainty that is suitable for many archaeological, ecological, environmental, and biological applications.

Acceptance Tests for AMS Radiocarbon Measurements at iThemba LABS, Gauteng, South Africa

The accelerator mass spectrometer was commissioned recently at the iThemba LABS 6 MV tandem accelerator. Improvements in the vacuum system, requiring procurement of cryo-pumps and the reducing the tank pressure of the N2 + CO2 insulation gas mixture below the level used for IBA measurements, were necessary. This resulted in the reduction of the nitrogen background and improved the resolution of 14C from 14N background in the ionisation chamber. The nitrogen was leaking to the stripping canal because of inadequate sealing. The analysing magnet was scaled to detect C3+ ions, at 3 MV terminal potential. The first sensible spectra allowed for the pin-pointing of many persistent issues. This resulted in measurements with a precision better than 1 pMC, and current blank levels correspond to 12 half-lives of 14C or ∼68000 years. The radiocarbon sample preparation laboratory has reached production status. A brief outlook of the work towards the implementation of the measurement and chemical preparation protocols for radionuclides 10Be and 26Al is also summarised in the conclusion

Radiocarbon Verification of the Earliest Astro-Chronological Datum

AbstractPapyri 10012A and 10012B from Illahun, Egypt, provide the earliest astro-chronological datum in history and, while calculated to various years in the 19th century BCE, have never been independently verified. As this datum enables the Middle Kingdom (MK) section of Egyptian historical chronology to be anchored in absolute time, it establishes the principal calendrical timeline for the eastern Mediterranean Bronze Age in the first half of the 2nd millennium BCE. AMS radiocarbon measurements of Papyrus 10012B establish its date range to 1886–1750 BCE, confirming the astronomical calculations and the essential reliability of Egyptian historical chronology for this period. Furthermore, all three leading estimates for the calendar year attribution of the document are supported by this analysis, with the role of a possible growing season effect determining which is most favored.

Landscape dynamics and human impact on high-mountain woodlands in the western Spanish Central System during the last three millennia

A multi-proxy palaeoenvironmental study (pollen, non-pollen palynomorphs, charcoal particles) of a mire, located in the western Spanish Central System (Gredos range), was undertaken to trace historic human activities related to woodland clearance and past land-uses at high altitudes during the last three millennia. The results of this study constrained by 4 AMS radiocarbon measurements are combined with archaeological data and compared with similar research carried out at the same altitude in mountains of central Iberia. The pollen data indicate that high-mountain areas were dominated by birch and pine woodlands until c. 2350years. From this date on a strong forest decline is recorded during the Late Iron Age and a deeper one c. 1500years ago in the Visigothic period, which may be related to increasing grazing activities and/or the occurrence of anthropogenic fires. Cereals and faba beans were cultivated in the surrounding valley since c. 2900cal BP, while chestnut, walnut and olive tree are documented mainly from the Roman period onwards.

Late Pleistocene and Holocene climatic variability in the Carpathian-Balkan region

ABSTRACTS VOLUMEGEOREVIEW From this perspective, a sedimentary lacustrine sequence located in the Eastern Carpathians,Northern Romania, has been subjected to multi-proxy analyses with the purpose ofreconstructing local environmental changes in response to climatic variability and human impact.The sequence (4 .1 m long) covering the last millennium is layered throughout and offers anexcellent opportunity for high-resolution past environmental reconstruction. The study site,ha, with 4.4 m maximum water depth (in 2010) (M indrescu et al., 2013). The lake catchment andsurrounding area (Fig. 1) are highly susceptible to slope movement due to their geology (i.e.,flysch), terrain gradients and climate parameters (heavy and prolonged rainfall, especially duringearly spring and summer; high soil moisture levels ensured by the generally cool climate). Methods and results The methods employed in this study are sediment geochemical characteristics (elementalcomposition, organic matter and carbonate content), physical properties (water content ofsediment, mineral magnetic properties, grain size), as well as biological indicators (treemacrofossils and pollen). The chronology of the entire sequence was established on four AMSradiocarbon measurements performed at Hertelendi Laboratory of Environmental Studies inDebrecen, Hungary (Fig. 2).

Lateglacial/Holocene transition to mid-Holocene: Vegetation responses to climate changes in the Apuseni Mountains (NW Romania)

Pollen datasets from central-eastern Europe, a region that for long time has been lacking quality palaeoecological records, are becoming increasingly available and these allow an evaluation of past vegetation sensitivity to climate change. Here, we use a new pollen and non-pollen palynomorph (NPP) record supported by eight AMS radiocarbon measurements from the Ic Ponor peat sequence, NW Romania, covering the end of the Lateglacial to mid-Holocene to examine the vegetation dynamics and associated climatic conditions. The vegetation at the Lateglacial to Holocene transition was composed of mixed forest (Pinus dominated) -tundra-steppe vegetation. Following the decline of Pinus from 11,200 cal BP, Ulmus and Picea abies expanded and formed dense forests, then by Corylus avellana and Quercus from 10,200 cal BP. The forests were mainly composed of C. avellana and P. abies along with Ulmus, Quercus and Fraxinus between 9800 and 7440 cal BP. Starting with 7200 cal BP, P. abies dominated the landscape in the area probably favored by the increasingly cooler and moist conditions. After a considerable hiatus between 5830 and 40 cal BP, the most recent changes in the forest composition in the area were primarily related to forest clearings and grazing. The absence of relevant occurrences of Fagus sylvatica and Carpinus betulus in our sequence prior to 8800 cal BP, fail to give support to the glacial survival of these two taxa in the Apuseni Mountains, as hypothesized in the previous pollen and genetic studies. However, their continuous occurrence in small percentages after 8800 cal BP most probably reflects locally present, small populations of these taxa. Short-term phases of changes in the vegetation composition that appeared to be the response to cooler and/or wetter climate were recorded between 11,800 and 11,700, 11,500–11,200, 10,300–10,200, 9350–9250, 8250–8140, 7700–7400, 6800–6600 and 6100–5900 cal BP. These intervals correlate well to other centennial-scale excursions recorded in Romania and Europe.

The Tienchi Pond on Lanyu Island (Western Pacific): Lake formation and potential as environmental archive

The formation, evolution, and potential as a climate archive of Tienchi Pond was evaluated using geomorphology, sedimentology, geochemistry, and AMS radiocarbon measurements of tree ring cores. Tienchi Pond is a small ephemeral lake situated on the subtropical Lanyu Island in the Western Pacific Ocean about 90km east of southern Taiwan. The lake is situated on a mountain ridge and is today characterized by numerous dead trees and stumps. The position at the boundary between the two main components of the SE Asian monsoon system, the Asian landmass and the Western Pacific, makes this lake particularly interesting as a potential natural climate archive.Since previous studies have shown that the bedrock underlying the lake formed over 2my ago, a volcanic crater origin was ruled out. Rather, element ratios of K/Ti and Ca/Fe together with 210Pb dating suggest a recent origin for the lake, probably as the result of a natural damming event in the southern, narrower, part of the lake basin, or as a result of increased precipitation at the end of the Little Ice Age (or a combination of both). Radiocarbon measurements on a dead tree near the lake perimeter show 14C levels of more than 1.7% modern radiocarbon near the bark, suggesting that the tree died in the early 1970s. In contrast, by correlating a large number of radiocarbon measurements to a northern hemisphere reference curve, it was shown that trees closer to the center of the lake died in the early 20th century. This agrees with a scenario where a small lake formed by initial damming, and gradually grew larger through erosion of the surrounding shore lines caused by rapid lake level oscillations.

Late Neanderthals at Jarama VI (central Iberia)?

Previous geochronological and archaeological studies on the rock shelter Jarama VI suggested a late survival of Neanderthals in central Iberia and the presence of lithic assemblages of Early Upper Paleolithic affinity. New data on granulometry, mineralogical composition, geochemical fingerprints and micromorphology of the sequence corroborate the previous notion that the archaeological units JVI.2.1 to JVI.2.3 are slackwater deposits of superfloods, which did not experience significant post-depositional changes, whereas the artifact-rich units JVI.3 and JVI.1 mainly received sediment inputs by sheetwash and cave spall. New AMS radiocarbon measurements on three samples of cut-marked bone using the ultrafiltration technique yielded ages close to, or beyond, the limit of radiocarbon dating at ca. 50 14C ka BP, and hence suggest much higher antiquity than assumed previously. Furthermore, elevated temperature post-IR IRSL luminescence measurements on K feldspars yielded burial ages for subunits JVI.2.2 and JVI.2.3 between 50 and 60ka. Finally, our reappraisal of the stone industry strongly suggests that the whole sequence is of Mousterian affinity. In conclusion, Jarama VI most probably does not document a late survival of Neanderthals nor an Early Upper Paleolithic occupation in central Iberia, but rather indicates an occupation breakdown after the Middle Paleolithic.

5년 간격 연륜의 위글매치를 이용한 정수사 법당 목부재의 방사성탄소연대 측정

연륜연대로 부여된 강화 정수사 법당 목부재(풍판)의 연대를 위글매치를 이용한 방사성탄소연대 측정결과와 비교하였다. 41년(AD 1250-1290) 연륜구간에서 1250년부터 5년 간격으로 9개 연륜에 대한 방사성탄소연대를 측정하였다. 개별 연륜에 대한 방사성탄소연대의 95.4% 신뢰구간은 113.3년(평균)에 달하였는데, 위글매치 후에는 20년으로 줄어들었다. 각 연륜의 방사성탄소연대 신뢰구간이 연륜연대값을 포함하여 연대의 정확성이 입증되었다. 이 결과는 위글매치를 이용한 방사성탄소연대 측정법이 우리나라 목재문화재의 연대측정에 효율적으로 쓰일 수 있음을 제시하고 있다. This paper reports the application of radiocarbon wiggle-matching for Korean wooden artifacts such as buildings and Buddhist statues for precise dating. Nine quinquennial (every five-year) samples of 41 years (AD 1250-1290) for AMS radiocarbon measurements were prepared from a wooden board used for the Main Hall at Jeongsusa (temple) in Kangwhado, Korea, which was dendrochronologically dated. The 95.4% confidence interval of radiocarbon dating prior to wiggle matching was 113.3 year in average. When wiggle-matching technique was applied, it became 20 years, 5.7 times smaller than that produced without wiggle matching. The results indicated that wiggle-matching technique using the calibration curve for northern hemisphere (IntCal04) can produce precise dates for Korean wooden artifacts, at least, for the <TEX>$13^{th}$</TEX> century.

Molecular sieve sampling of CO2 from decomposition of soil organic matter for AMS radiocarbon measurements

K. Hamalainen, H. Fritze, H. Jungner, K. arhu, M. Oinonen, E. Sonninen, P. Spetz, M. Tuomi, P. Vanhala, and J. Liski, 'Molecular sieve sampling of CO2 from decomposition of soil organic matter for AMS radiocarbon measurements', Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Vol. 268 (7-8): 1067-1069, first published online 8 October 2009. The version of record is available at doi: http://dx.doi.org/10.1016/j.nimb.2009.10.099 Copyright © 2009 Elsevier B.V. All rights reserved.

Investigating the likelihood of a reservoir offset in the radiocarbon record for ancient Egypt

Some radiocarbon dates for ancient Egypt have been significantly offset from the established historical chronology (see Bonani et al., 2001). In this paper, short-lived plant species collected in Egypt between 1700 and 1900 AD were used to investigate the possibility that the radiocarbon record had been influenced by reservoir effects. AMS radiocarbon measurements were made on 66 known-age samples, resulting in an average offset from expected values of 19 years. The implications of this minor discrepancy on the likelihood of a reservoir process are discussed, and the agreement of the data with recent models of radiocarbon seasonality is also considered.

Caribbean sclerosponge radiocarbon measurements re-interpreted in terms of U/Th age models

Previously unpublished AMS radiocarbon measurements of a sclerosponge from tongue of the ocean (TOTO), Bahamas, as well as preliminary data from an investigation of the radiocarbon records of sclerosponges living at different depths in the adjacent Bahamas basin, Exuma Sound, are interpreted in terms of U-series age models. The data are compared to an existing Caribbean sclerosponge radiocarbon bomb curve measured using standard gas proportional beta counting and used to interpret a 210Pb age model. The Δ14C records from the sclerosponges illustrate a potential for use of radiocarbon both as a tracer of subsurface water masses or as an additional age constraint on recently sampled sclerosponges. By using an independent age model, this study lays the framework for utilizing sclerosponges from different locations in the tropics and subtropics and different depths within their wide depth range (0–250m) to constrain changes in production of subtropical underwater in the Atlantic Ocean. This framework is significant because the proxy approach is necessary to supplement the short and coarse time series being used to constrain variability in the formation of Caribbean subtropical underwater, the return flow of a shallow circulation cell responsible for nearly 10% of the heat transported poleward in the N. Atlantic.

Holocene forest dynamics in northwestern Romnania

Pollen analyses and AMS radiocarbon measurements were carried out on peat deposits from the former crater lake Preluca Tiganului, located in a mid-altitude area of the Gutaiului Mountains (NW Romania), in order to reconstruct the postglacial vegetation history. At the Lateglacial/Holocene transition the open vegetation was replaced by forest, suggesting a fast response to climatic warming. The rapid expansion of Pinus, Betula and later Picea may be due to their existence in the area during the Lateglacial. At approximately 11 250 cal. yr BP, the dense forest was composed primarily of Ulmus and some Picea, Betula and Pinus. A small population of Ulmus might also have survived in the area during the Lateglacial. At 10750 cal. yr BP, Quercus, Tilia and Fraxinus, followed by Corylus at c. 10200 cal. yr BP, expanded significantly in the forest. The delay of approximately 550 years in their establishment, as compared to the expansion of Ulmus, was probably due to their immigration from more distant localities. Between 9300 and 5750 cal. yr BP, the forest became denser and was composed of Corylus (dominating), Ulmus, Quercus, Tilia, Fraxinus and Picea. At 5750 cal. yr BP Carpinus became established and expanded, possibly as a response to higher temperatures. At 5200 cal. yr BP, Fagus became locally established, and expanded from about 4800 cal. yr BP, possibly as a result of moist climatic conditions, although human activities cannot be excluded. From 4000 cal. yr BP to the present, Fagus dominated the woodlands, and all other deciduous trees (except for Carpinus and Quercus) became greatly reduced. Evidence of human influence on the local vegetation is low for this time period, but becomes more evident in the pollen stratigraphy around 2300 cal. yr BP. This is reflected by a decrease in forest diversity and an increase in pasture and forest grazing.