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Speed Dating: A Rapid Way to Determine the Radiocarbon Age of Wood by EA-AMS
Abstract
Radiocarbon measurements in tree rings can be used to estimate atmospheric 14 C concentration and thereby used to create a 14 C calibration curve. When wood is discovered in construction sites, rivers, buildings, and lake sediments, it is unclear if the wood could fill gaps in the 14 C calibration curve or if the wood is of historical interest until the age is determined by dendrochronology or 14 C dating. However, dendrochronological dating is subjected to many requirements and 14 C dating is costly and time consuming, both of which can be frivolous endeavors if the samples are not in the age range of interest. A simplified 14 C dating technique, called Speed Dating, was thus developed. It can be used to quickly obtain 14 C ages as wood samples are neither chemically treated nor graphitized. Instead, wood is combusted in an elemental analyzer (EA) and the CO 2 produced is carried into an accelerator mass spectrometer (AMS) with a gas ion source. Within a day, 75 samples can be measured with uncertainties between 0.5–2% depending on the age, preservation, and contaminants on the material and Speed Dating costs about one-third of conventional AMS dates.
... While all samples agree within a 1 σ interval, smaller samples bear larger uncertainties that are due to counting statistics. AMS measurements rely on direct counting of 14 C atoms present in the sample, which for samples > 200 μg C allows precision down to 2‰ error [62], whereas samples below 100 μg C typically yield uncertainties ranging between 0.5 to 2% [63,64]. These errors increase further from constant contamination because of error propagation (Additional file 1: Table S6). ...
The accessioning of ancient textiles into museum collections often requires objective information regarding the object’s appropriateness and authenticity before purchase or gift acceptance. In the case of colored fabrics, the identification of dyestuffs consistent with the attributed time period and culture builds confidence and reduces the chances of the object being a simple forgery or fake produced using modern materials. Moreover, this information adds to the technical, cultural, and conservation knowledge regarding the object. Increasingly, chronometric age estimates in the form of radiocarbon dating are also needed to establish the object’s age or to further prove the materials match the purported date range of the textile. Each of these analyses consumes a small sample of the object, and typically they are conducted separately by different laboratories on individual sample yarns. This report demonstrates for the first time the sequential, combined analysis of dyes by liquid chromatography-diode array detection-mass spectrometry and radiocarbon dating of the same residual dye-extracted sample. The chemicals and solvents used in various dye extraction protocols are shown not to contaminate the extracted yarns for radiocarbon dating purposes. The approach was used in the authentication study of an ancient Nazca tunic made from natural fibers (wool) and dyes (indigoids, anthraquinones, and flavonoids) shown to have most likely been produced between 595 and 665 CE.
... The floating chronologies were roughly bound to the calendar time using radiocarbon dating. A total of 166 subfossil wood samples from Yamal were dated at different times by the radiocarbon method: 53 of them at the Institute of Plant and Animal Ecology, Ural Branch, Russian Academy of Sciences, and at the University of Bern [18], and 113 at the Laboratory of Ion Beam Physics, ETH Zurich (13 samples by the AMS method and 100 samples by the speed dating method [19]). ...
... Indeed, using AMS technology, the 14 C atoms present in a sample are directly counted. While graphitized samples (0.2-1 mg of C) can provide high precision results down to 2‰ error 30,31 , gas targets are typically measured on less than 100 µg C with uncertainties ranging between 0.5 and 2% depending on the age of the sample 24,25,32,33 . A comparison of graphite and gas 14 C age uncertainties conducted on foraminifera show that above 40 µg C age uncertainties increase as a function of increasing 14 C age only, while below 40 µg C the decreasing sample size also plays a role 34 . ...
Recently, radiocarbon dating underwent considerable technological advances allowing unprecedented sample size downscaling. These achievements introduced novel opportunities in dating cultural heritage objects. Within this pioneering research, the possibility of a direct 14C dating of lead white pigment and organic binder in paint samples was investigated on polychrome sculptures, a foremost artistic expression in human history. The polychromy, an indivisible part of polychrome sculpture, holds a key role in the interpretation and understanding of these artworks. Unlike in other painted artworks, the study of polychromies is repeatedly hampered by repaints and degradation. The omnipresence of lead white within the original polychromy was thus pursued as dating proxy. Thermal decomposition allowed bypassing geologic carbonate interferences caused by the object's support material, while an added solvent extraction successfully removed conservation products. This radiocarbon dating survey of the polychromy from 16 Portuguese medieval limestone sculptures confirmed that some were produced within the proposed chronologies while others were revised. Within this multidisciplinary study, the potential of radiocarbon dating as a complementary source of information about these complex paint systems guiding their interpretation is demonstrated. The challenges of this innovative approach are highlighted and improvements on sampling and sample preparation are discussed.
... The ion source of the MICADAS is also capable of accepting CO 2 gas using the Gas Interface System (Ruff et al. 2010;Wacker et al. 2013a). This feature can be used to analyze microgram amounts of carbon (Haghipour et al. 2019), "Speed Dating" for rangefinder ages (Sookdeo et al. 2017), and jointly determine δ 13 C and 14 C ages with an EA-IRMS-MICADAS coupling . The Chronos facility is equipped with a GIS and future testing is planned to integrate this form of measurement into our procedures. ...
The Chronos ¹⁴ Carbon-Cycle Facility is a new radiocarbon laboratory at the University of New South Wales, Australia. Built around an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) Accelerator Mass Spectrometer (AMS) installed in October 2019, the facility was established to address major challenges in the Earth, Environmental and Archaeological sciences. Here we report an overview of the Chronos facility, the pretreatment methods currently employed (bones, carbonates, peat, pollen, charcoal, and wood) and results of radiocarbon and stable isotope measurements undertaken on a wide range of sample types. Measurements on international standards, known-age and blank samples demonstrate the facility is capable of measuring ¹⁴ C samples from the Anthropocene back to nearly 50,000 years ago. Future work will focus on improving our understanding of the Earth system and managing resources in a future warmer world.
... (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) 2013; Sookdeo et al., 2017), and traditional high-precision radiocarbon dating methods (Longworth et al., 2015) at the National Ocean Sciences Accelerator Mass Spectrometer (NOSAMS) facility at Woods Hole Oceanographic Institution. The reconnaissance analysis was performed after initial sample collection in order to obtain approximate estimates of age. ...
Tree-rings provide precise annually dated climate information, but their application can be limited by the relatively short lifespan of many trees. To overcome this limitation, tree-ring records can be extended over longer time periods by connecting living trees with older “sub-fossil” trees, which can provide information on longer timescales throughout the Holocene. These long chronologies are proxy records of past climate, provide precise chronological information for extreme events, and give insight into the range of natural climate variability prior to the instrumental period. In the densely populated northeastern United States, few tree-ring records are longer than 500 years, and there are no millennial-length tree-ring chronologies for the region. Here, we use a combination of standard dendrochronological and radiocarbon techniques, including use of the 774 CE radiocarbon excursion, to generate an absolutely dated 2500 year-long tree ring record from living, archaeological, and subfossil Atlantic white cedar (Chamaecyparis thyoides) found in the coastal northeastern United States. Our chronology demonstrates the potential to develop multi-millennial Chamaecyparis thyoides tree-ring records to address previously unanswered questions regarding late Holocene hydroclimate, extreme events, and temperature variability in New England.
... Process blanks, reference material and samples were chemically treated to extract cellulose. Cellulose is a component of wood that has remained unchanged over time and can be used for an accurate 14 C-date (Hoper et al. 1998;Brock et al. 2010;Sookdeo et al. 2017). Cellulose was extracted in batches of 56 (2 TK121, 2 BK, 2 KB and 50 samples) using a modified base-acid-base-acid-bleaching method outlined by Němec et al. (2010). ...
Advances in accelerator mass spectrometry have resulted in an unprecedented amount of new high-precision radiocarbon ( ¹⁴ C) -dates, some of which will redefine the international ¹⁴ C calibration curves (IntCal and SHCal). Often these datasets are unaccompanied by detailed quality insurances in place at the laboratory, questioning whether the ¹⁴ C structure is real, a result of a laboratory variation or measurement-scatter. A handful of intercomparison studies attempt to elucidate laboratory offsets but may fail to identify measurement-scatter and are often financially constrained. Here we introduce a protocol, called Quality Dating, implemented at ETH-Zürich to ensure reproducible and accurate high-precision ¹⁴ C-dates. The protocol highlights the importance of the continuous measurements and evaluation of blanks, standards, references and replicates. This protocol is tested on an absolutely dated German Late Glacial tree-ring chronology, part of which is intercompared with the Curt Engelhorn-Center for Archaeometry, Mannheim, Germany (CEZA). The combined dataset contains 170 highly resolved, highly precise ¹⁴ C-dates that supplement three decadal dates spanning 280 cal. years in IntCal, and provides detailed ¹⁴ C structure for this interval.
... During the 14th International AMS Conference held in Ottawa, Canada (August 14-18, 2017) and the 23rd International Radiocarbon Conference in Trondheim, Norway (June 17-22, 2018), Ionplus AG and MICADAS AMS users reported the advantages and applications of this small (0.2 MV) but effective AMS system. Now, coupled with an automatic graphitization device (e.g., AGE 3 and CH2) and a gas ion-source interface, a small AMS like MICADAS is able to conduct rapid radiocarbon dating on 100 μg C of organic and inorganic nature, as well as from CO 2 gas directly (Sookdeo et al., 2016;Tuna et al., 2018). This development of AMS technology, aided by judicial sample selection, sample pretreatment and laboratory work, certainly benefits more and more radiocarbon applications. ...
... Recently, a method using an elemental analyzer combined with the AGE (EA-AGE method) has been applied to some types of samples (e.g. cellulose, bone collagen) (Cersoy et al. 2017;Sookdeo et al. 2017;Fewlass et al. 2018). ...
We conducted a preliminary test of the coupled system of an elemental analyzer and the automated graphitization equipment Ionplus AGE3 (EA-AGE3 method) for accelerator mass spectrometry radiocarbon (AMS ¹⁴ C) measurements of CaCO 3 samples, by comparing with the conventional method where the samples are hydrolyzed in phosphoric acid and resulting CO 2 gas is manually graphitized in a vacuum line (HPA method). The samples used in the test were the IAEA C2 travertine, fossil and modern corals from the Ryukyu Islands and the Ogasawara Islands, respectively (both are located in the northwestern subtropical Pacific). Results indicate that, relative to the HPA method, the EA-AGE3 method tends to cause an increase of ~0.4–0.5 pMC with more widely scattered data. This is presumably due to ¹⁴ C contamination in the EA (the most likely cause seems to be a memory effect of ¹⁴ C); this effect could be reduced by careful optimization of conditions and procedures in the EA process. The ¹⁴ C data of pre-bomb annual bands (1931–1949 AD) in the modern Ogasawara coral obtained by the HPA method were used to estimate the marine reservoir ¹⁴ C-age correction (ΔR) of this region; it ranges from –109 yr to –28 yr with the mean value with standard deviation of –81 ± 29 yr.
... The methods of chemical pretreatment of wood for 14 C dating, including high accuracy dating, were examined and described by numerous authors (e.g. Hoper et al. 1998;Bird et al. 1999;Santos et al. 2001;Anchukaitis et al. 2008;Nemec et al. 2010;Southon and Magana 2010;Santos and Ormsby 2013;Staff et al. 2014, Wacker et al. 2014Hajdas et al. 2016;Sookdeo et al. 2016). Also, the authors of this article had decided to conduct their own tests, carried out in three Polish laboratories (Gliwice, Kraków, and Poznań). ...
Our project aimed to construct a Scots Pine ( Pinus sylvestris L.) chronology for part of the Late Glacial and reconstruct changes in the ¹⁴ C concentrations during this period. Kwiatków (Kolska Basin, central Poland) proved to be very prospective site, in which wood from the end of Allerød was recognized. A level of organic deposits with so-called fossil forest was encountered within the late-Vistulian terrace of the low valley of the Warta river. Dendrochronological analysis of over 267 samples complying to the requirements of the method allowed, at the present stage of the research, to construct a chronology spanning 265 yr. Fifty-two samples (5 consecutive rings each) were subjected to α-cellulose extraction and ¹⁴ C measurements. Ninety-six results and the wiggle-matching technique anchor the chronology to the period 13,821–13,561 cal BP (A comb =141.6%) according to the D_Sequence procedure and the IntCal13 calibration curve or to 13,800–13,540 cal BP according to the wiggle-matching technique using the χ ² test and raw data, i.e. the Heidelberg tree-ring sequence.
... The choice of wood preparation method for high resolution 14 C measurements is often a compromise between minimizing material loss and separation of the least-mobile wood component which best reflects the initial state (content of 14 C isotope) at the moment of ring formation. A number of studies have been carried out on wood preparation for 14 C measurements (Anchukaitis et al., 2008;Bird et al., 1999;Hajdas et al., 2016;Hoper et al., 1998; et al., 2001;Santos and Ormsby, 2013;Sookdeo et al., 2016;Southon and Magana, 2010). In this study the authors decided to test different types of wood preparation methods. ...
An analysis was performed on samples from a series of well-preserved tree trunks and in situ stumps of Allerød/Younger Dryas age found in Koźmin and Kwiatków, Kolska Basin, Central Poland. Five different types of wood preparation methods were investigated in three Polish radiocarbon laboratories (Gliwice, Poznań and Krakow) in order to find the most stable, repeatable and reliable procedure. Their effect was tested on the stable carbon isotope ratio (δ¹³C) and ¹⁴C age. Additionally, FTIR spectroscopy was used as a simple technique for obtaining rapid information on the structure of wood constituents and chemical changes taking place in wood due to various chemical treatments. The results of AMS measurements did not show statistically significant differences in radiocarbon ages of samples prepared according to the tested methods. On the other hand, δ¹³C measurements showed that the smallest scattering results gave α-cellulose obtained by the method BABA + Bleaching (with NaClO2 and HCl) + strong base. Moreover, the mean δ¹³C values for holo-cellulose samples are higher than those for α-cellulose samples. Studies evidenced that the methods of preparation leading to holo- or α-cellulose gave the same FTIR spectra, while the standard method of the chemical pretreatment of samples for ¹⁴C measurements (ABA) preceded by mercerization is insufficient for removing compounds containing aromatic rings.
... Performed at the Laboratory of Ion Beam Physics, ETH-Zurich, both the well-established high-precision 14 C Accelerator Mass Spectrometer (AMS) dating (Synal et al., 2007;Wacker et al., 2014Wacker et al., , 2010, as well as the novel 'Speed Dating' (Sookdeo et al., 2016), were used for radiocarbon dating (Güttler et al., 2015(Güttler et al., , 2013N emec et al., 2010). While high-resolution AMS-dating ( ±20e25-year 1sigma) can reveal accurate tree ages along the IntCal13 calibration curve , the simplified 'Speed Dating' technique provides rough estimates of the expected age range. ...
The rate and magnitude of temperature variability at the transition from the Last Glacial Maximum into the early Holocene represents a natural analog to current and predicted climate change. A limited number of high-resolution proxy archives, however, challenges our understanding of environmental conditions during this period. Here, we present combined dendrochronological and radiocarbon evidence from 253 newly discovered subfossil pine stumps from Zurich, Switzerland. The individual trees reveal ages of 41–506 years and were growing between the Allerød and Preboreal (∼13′900–11′300 cal BP). Together with previously collected pines from this region, this world's best preserved Late Glacial forest substantially improves the earliest part of the absolutely dated European tree-ring width chronology between 11′300 and 11′900 cal BP. Radiocarbon measurements from 65 Zurich pines between ∼12′320 and 13′950 cal BP provide a perspective to prolong the continuous European tree-ring record by another ∼2000 years into the Late Glacial era. These data will also be relevant for pinpointing the Laacher See volcanic eruption (∼12′900 cal BP) and two major Alpine earthquakes (∼13′770 and ∼11′600 cal BP). In summary, this study emphasizes the importance of dating precision and multi-proxy comparison to disentangle environmental signals from methodological noise, particularly during periods of high climate variability but low data availability, such as the Younger Dryas cold spell (∼11′700 and 12′900 cal BP).
... It should be noted in this regard that the Lake Gerber sampling site in the Spanish central Pyrenees still provides some potential to extend the composite chronology further back in time. There still remain ample subfossil trunks preserved in several smaller and larger lakes between 2100 and 2400 m MSL although to recover them will be costly, calling for professional diving campaigns, as well as numerous high-precision 14 C dates in addition to conventional tree-ring dating (Sookdeo et al. 2017). ...
Paleoclimatic evidence is necessary to place the current warming and drying of the western Mediterranean basin in a long-term perspective of natural climate variability. Annually resolved and absolutely dated temperature proxies south of the European Alps that extend back into medieval times are, however, mainly limited to measurements of maximum latewood density (MXD) from high-elevation conifers. Here, the authors present the world’s best replicated MXD site chronology of 414 living and relict Pinus uncinata trees found .2200 m above mean sea level (MSL) in the Spanish central Pyrenees. This composite record correlates significantly (p # 0.01) with May–June and August–September mean temperatures over most of the Iberian Peninsula and northern Africa (r 5 0.72; 1950–2014). Spanning the period 1186–2014 of the Common Era (CE), the new reconstruction reveals overall warmer conditions around 1200 and 1400, and again after around 1850. The coldest reconstructed summer in 1258 (24.48C compared to 1961–90) followed the largest known volcanic eruption of the CE. The twentieth century is characterized by pronounced summer cooling in the 1970s, subsequently rising temperatures until 2003, and a slowdown of warming afterward. Little agreement is found with climate model simulations that consistently overestimate recent summer warming and underestimate preindustrial temperature changes. Interannual–multidecadal covariability with regional hydroclimate includes sum- mer pluvials after large volcanic eruptions. This study demonstrates the relevance of updating MXD-based temper- ature reconstructions, not only back in time but also toward the present, and emphasizes the importance of comparing temperature and hydroclimatic proxies, as well as model simulations for understanding regional climate dynamics.
In this study we aim to identify the optimal cellulose extraction protocol for 14C dating of wood, with a focus on glacial trees. To achieve this, we compare three cellulose extraction methods on the basis of cellulose yield and 14C age. The study is conducted on 12 wood samples of different species, in varying states of preservation with ages covering the full 14C age range. Cellulose is extracted from each sample following three different protocols selected from the literature: ABA-B, BABAB and 2Chlorox. The extracted cellulose was graphitised and dated with the MICADAS (Mini Carbon Dating System) at the ETH AMS laboratory. Although all three methods are considered efficient, the BABAB protocol, despite being a more aggressive procedure, allows the extraction of a sufficient amount of cellulose to be 14C dated and leads to the most reliable results, particularly for very old and background samples (samples with 14C content of zero).
We present a new low-cost, high-throughput method for converting many types of organic carbon samples into graphite for radiocarbon ( ¹⁴ C) measurements by accelerator mass spectrometry (AMS). The method combines sample combustion and reduction to graphite into a single procedure. In the Single Step method, solid samples are placed directly into Pyrex containing zinc, titanium hydride and iron catalyst. The tube is evacuated, flame sealed, and placed in a muffle furnace for 7 hr. A variety of organic samples have been tested including oxalic acid, sucrose, wood, peat, collagen, humic acid, and contamination swipe samples. The method significantly reduces the time required to produce a graphite sample for ¹⁴ C measurement, with analytical precision and accuracy approaching that of traditional two-step combustion and hydrogen reduction methods. The details and applicability of the method are presented.
The combined oak and pine tree-ring chronologies of Hohenheim University are the backbone of the Holocene radiocarbon calibration for central Europe. Here, we present the revised Holocene oak chronology (HOC) and the Preboreal pine chronology (PPC) with respect to revisions, critical links, and extensions. Since 1998, the HOC has been strengthened by new trees starting at 10,429 BP (8480 BC). Oaks affected by cockchafer have been identified and discarded from the chronology. The formerly floating PPC has been cross-matched dendrochronologically to the absolutely dated oak chronology, which revealed a difference of only 8 yr to the published 14 C wiggle-match position used for IntCal98. The 2 parts of the PPC, which were linked tentatively at 11,250 BP, have been revised and strengthened by new trees, which enabled us to link both parts of the PPC dendrochronologically. Including the 8-yr shift of the oak-pine link, the older part of the PPC (pre-11,250 BP) needs to be shifted 70 yr to older ages with respect to the published data (Spurk 1998). The southern German part of the PPC now covers 2103 yr from 11,993–9891 BP (10,044–7942 BC). In addition, the PPC was extended significantly by new pine chronologies from other regions. A pine chronology from Avenches and Zürich, Switzerland, and another from the Younger Dryas forest of Cottbus, eastern Germany, could be crossdated and dendrochronologically matched to the PPC. The absolutely dated tree-ring chronology now extends back to 12,410 cal BP (10,461 BC). Therefore, the tree-ring-based 14 C calibration now reaches back into the Central Younger Dryas. With respect to the Younger Dryas-Preboreal transition identified in the ring width of our pines at 11,590 BP, the absolute tree-ring chronology now covers the entire Holocene and 820 yr of the Younger Dryas.
The Southern Hemisphere SHCal04 radiocarbon calibration curve has been updated with the addition of new data sets extending measurements to 2145 cal BP and including the ANSTO Younger Dryas Huon pine data set. Outside the range of measured data, the curve is based upon the ern Hemisphere data sets as presented in IntCal13, with an interhemi-spheric offset averaging 43 ± 23 yr modeled by an autoregressive process to represent the short-term correlations in the offset.
The Southern Hemisphere SHCal04 radiocarbon calibration curve has been updated with the addition of new data sets extending measurements to 2145 cal BP and including the ANSTO Younger Dryas Huon pine data set. Outside the range of measured data, the curve is based upon the ern Hemisphere data sets as presented in IntCal13, with an interhemi-spheric offset averaging 43 ± 23 yr modeled by an autoregressive process to represent the short-term correlations in the offset.
In 2010 more than 600 radiocarbon samples were measured with the gas ion source at the MIni CArbon DAting System (MICADAS) at ETH Zurich and the number of measurements is rising quickly. While most samples contain less than 50 μg C at present, the gas ion source is attractive as well for larger samples because the time-consuming graphitization is omitted. Additionally, modern samples are now measured down to 5 per-mill counting statistics in less than 30 min with the recently improved gas ion source.In the versatile gas handling system, a stepping-motor-driven syringe presses a mixture of helium and sample CO2 into the gas ion source, allowing continuous and stable measurements of different kinds of samples. CO2 can be provided in four different ways to the versatile gas interface. As a primary method, CO2 is delivered in glass or quartz ampoules. In this case, the CO2 is released in an automated ampoule cracker with 8 positions for individual samples. Secondly, OX-1 and blank gas in helium can be provided to the syringe by directly connecting gas bottles to the gas interface at the stage of the cracker. Thirdly, solid samples can be combusted in an elemental analyzer or in a thermo-optical OC/EC aerosol analyzer where the produced CO2 is transferred to the syringe via a zeolite trap for gas concentration. As a fourth method, CO2 is released from carbonates with phosphoric acid in septum-sealed vials and loaded onto the same trap used for the elemental analyzer. All four methods allow complete automation of the measurement, even though minor user input is presently still required. Details on the setup, versatility and applications of the gas handling system are given.
The IntCal09 and Marine09 radiocarbon calibration curves have been revised utilizing newly available and updated data sets from 14C measurements on tree rings, plant macrofossils, speleothems, corals, and foraminifera. The calibration curves were derived from the data using the random walk model (RWM) used to generate IntCal09 and Marine09, which has been revised to account for additional uncertainties and error structures. The new curves were ratified at the 21st International Radiocarbon conference in July 2012 and are available as Supplemental Material at www.radiocarbon.org. The database can be accessed at http://intcal.qub.ac.uk/intcal13/. © 2013 by the Arizona Board of Regents on behalf of the University of Arizona.
The novel tabletop miniaturized radiocarbon dating system (MICADAS) at ETH Zurich features a hybrid Cs sputter negative ion source for the measurement of solid graphite and gaseous CO2 samples. The source produces stable cur- rents of up to 6 µA C- out of gaseous samples with an efficiency of 3-6%. A gas feeding system has been set up that enables constant dosing of CO2 into the Cs sputter ion source and ensures stable measuring conditions. The system is based on a syringe in which CO2 gas is mixed with He and then pressed continuously into the ion source at a constant flow rate. Mini- mized volumes allow feeding samples of 3-30 µg carbon quantitatively into the ion source. In order to test the performance of the system, several standards and blanks have successfully been measured. The ratios of 14C/12C could be repeated within statistical errors to better than 1.0% and the 13C/12C ratios to better than 0.2%. The blank was
In this paper, we summarize the main chemical pretreatment protocols currently used for AMS radiocarbon dating at the Oxford Radiocarbon Accelerator Unit, updating the protocols last described by Hedges et al. (1989). © 2010 by the Arizona Board of Regents on behalf of the University of Arizona.
In a separate study, we conducted a series of high-precision radiocarbon measurements using wood from Britain and New Zealand to investigate interhemispheric offsets and possible temporal variations. To minimize variability associated with different species, the pretreatment of the oak (Quercus patraea) and cedar (Librocedrus bidwilli) was to acellulose for both. This study investigates the thoroughness of a range of pretreatment processes by the stable isotope analysis of the products. This article has been published in the journal: Radiocarbon. © 1998 the Arizona Board of Regents on behalf of the University of Arizona. Used with permission.
The novel tabletop miniaturized radiocarbon dating system (MICADAS) at ETH Zurich features a hybrid Cs sputter negative ion source for the measurement of solid graphite and gaseous CO 2 samples. The source produces stable currents of up to 6 μA C − out of gaseous samples with an efficiency of 3–6%. A gas feeding system has been set up that enables constant dosing of CO 2 into the Cs sputter ion source and ensures stable measuring conditions. The system is based on a syringe in which CO 2 gas is mixed with He and then pressed continuously into the ion source at a constant flow rate. Minimized volumes allow feeding samples of 3–30 μg carbon quantitatively into the ion source. In order to test the performance of the system, several standards and blanks have successfully been measured. The ratios of 14 C/ 12 C could be repeated within statistical errors to better than 1.0% and the 13 C/ 12 C ratios to better than 0.2%. The blank was <1 pMC.
The prototype mini carbon dating system (MICADAS) at ETH Zurich has been in routine operation for almost 2 yr. Because of its simple and compact layout, setting up a radiocarbon measurement is fast and the system runs very reliably over days or even weeks without retuning. The stability of the instrument is responsible for the good performance in highest-precision measurements where results of single samples can be reproduced within less than 2‰. The measurements are described and the performance of MICADAS is demonstrated on measured data.
In the best case, radiocarbon measurements allow artificial objects to be dated with a precision of 10 calendar years when conventional wiggle-matching onto the IntCal09 calibration curve is applied. More precise dating can only be achieved by using annually resolved 14 C calibration data, particularly in timespans when there are rapid changes in atmospheric 14 C concentration. The recently observed jump in atmospheric 14 C concentration of 1.5% between AD 774 and 775, though expected to be rare, is a good example for such a rapid change. We demonstrate by example that is possible to precisely 14 C date the cutting year of a timber in the historically important and well-preserved Holy Cross chapel of the convent St. John the Baptist in Val Müstair, Switzerland.
This paper reports on the performance of a new method of sample injection using the High Voltage Engineering Europa (HVEE) SO-110 ion source jointly developed between HVEE and Oxford. In order to use this source, we have developed a new gas handling system which works on the direct injection of carbon dioxide mixed into a continuous flow of helium. Preliminary work has also been carried out on online gas chromatography-accelerator mass spectrometry (GC-AMS). In this application, a GC is directly coupled to the AMS system using a GC-IRMS combustion interface and Nafion ™ drier. We show here results for the measurement of natural abundance in separated compounds with good peak separation and precisions of about 10%. This type of system should be ideal for source apportionment studies, biomedical, and other similar work where high precision is not required but where sample sizes are very low.
Traditionally tree ring analysis has been used for dating structures and reconstructing past climates. Recently it has been recognised as a valuable tool in detecting environmental change. This wide-ranging review of current knoledge is organised around six chapters, each of them with from 5-11 sections contributed by different authors: the authors are drawn from all over the world and have knowledge of both Northern and Southern Hemispheres. Appendix A lists tree species known to have been used to build tree-ring chronologies, Appendix B provides a sample site and tree information form for tree ring collections, and Appendix C lists sources of tree ring analytical programs and measuring stages. The consolidated bibliography (pp 351-391) totals about 650 references. The addresses of all authors are given on pp 393-394. -K.Clayton
In the best case, radiocarbon measurements allow artificial objects to be dated with a precision of 10 calendar years when conventional wiggle-matching onto the IntCal09 calibration curve is applied. More precise dating can only be achieved by using annually resolved ¹⁴C calibration data, particularly in timespans when there are rapid changes in atmospheric ¹⁴C concentration. The recently observed jump in atmospheric ¹⁴C concentration of 1.5% between AD 774 and 775, though expected to be rare, is a good example for such a rapid change. We demonstrate by example that is possible to precisely ¹⁴C date the cutting year of a timber in the historically important and well-preserved Holy Cross chapel of the convent St. John the Baptist in Val Müstair, Switzerland.
DOI: 10.2458/56.17634
An on-line measurement system was installed at the MICADAS in Zurich, using an elemental analyzer (EA) as a combustion unit to enable direct radiocarbon measurement of samples containing carbon in the range of 5-100 μg possible with minimum effort. The samples are combusted in small capsules and the gaseous combustion products are separated by the EA. The carbon dioxide leaving the EA in a high helium flow is concentrated on a small external trap containing X13 zeolite adsorber material. This new concept, avoiding a cryogenic trapping for the enrichment step, allows the construction of a very compact system able to work even with the smallest samples. Concentrated on the external trap, the carbon dioxide is flushed into the gas-tight syringe of our gas inlet system using a low helium stream. The gas mixture is measured with the MICADAS gas ion source. Several different sample capsules were analyzed to minimize the major blank contribution coming from the sample vessel. The best results were achieved with 25-μL tin capsules, which contained only 0.34 ± 0.13 μg carbon at 65 pMC. This work describes the development of the on-line system and the protocol for measurement runs. Results are presented for on-line measurements of reference materials and a comparison is performed with typical dating samples measured previously as graphite targets. Finally, relevance and limitations of on-line measurements are discussed. © 2010 by the Arizona Board of Regents on behalf of the University of Arizona.
The reaction conditions for the graphitization of CO2 with hydrogen were optimized for a fast production of high-quality carbon samples for accelerator mass spectrometry (AMS) measurement. The iron catalyst in use is first oxidized by heating with air to remove possible carbon and other impurities and then after evacuation reduced back to iron with hydrogen in several flushing steps to remove any iron oxide. The optimum conditions for a fast graphitization reaction were experimentally determined by changing the reaction temperatures and the H-2/CO2 ratio. The resulting graphite samples were measured by AMS to find the smallest isotopic changes (delta C-13) at a minimum of molecular fragment formation ((CH)-C-13 current). The improvements are based on thermodynamic data and are explained with Baur-Glaessner diagrams.
For more than 4 years, gaseous samples of 1–50 μg carbon have been routinely measured with the gas ion source of the small AMS (Accelerator Mass Spectrometer) facility MICADAS (MIni CArbon DAting System) at ETH Zurich. The applied measurement technique offers a simple and fast way of 14C measurements without the need of sample graphitization. A major drawback of gaseous 14C measurements, however, is the relatively low negative ion current, which results in longer measurement times and lower precision compared to graphitized samples. In December 2009, a new, improved Cs sputter ion source was installed at MICADAS and we began to optimize conditions for the measurement of gaseous samples. 12C− currents from the new ion source were improved from initially 3 to 12–15 μA for routine measurements and the negative ion yield was increased by a factor of 2, reaching 8% on average during routine operation. Moreover, the new measurement settings enable a doubled CO2 flow, thus substantially reducing measurement times. The achieved performance allows closing the sample size gap between gaseous and solid samples and makes the gas ion source a promising tool for dating with a measurement precision of 5‰ on samples as small as 50 μg carbon.
Here we present the entire range of Lateglacial tree-ring chronologies from Switzerland, Germany, France, covering the Lateglacial north and west of the Alps without interruption as well as finds from northern Italy, complemented by a 14C data set of the Swiss chronologies. Geographical expansion of cross-matched European Lateglacial chronologies, limits and prospects of teleconnection between remote sites and extension of the absolute tree-ring chronology are discussed. High frequency signals and long-term fluctuations are revealed by the ring-width data sets of the newly constructed Swiss Late-glacial Master Chronology (SWILM) as well as the Central European Lateglacial Master Chronology (CELM) spanning 1606 years. They agree well with the characteristics of Boelling/Alleroed (GI-1) and the transition into Younger Dryas (GS-1). The regional chronologies of Central Europe may provide improved interconnection to other terrestrial or marine high-resolution archives. Nevertheless the breakthrough to a continuous absolute chronology back to Boelling (GI-1e) has not yet been achieved. A gap remains, even though it is covered by several floating chronologies from France and Switzerland.
A method for interfacing an automated combustion unit to a gas ion source for 14C analysis is described. This method makes use of an actively controlled transfer line which accommodates the relatively fast flow of the output He carrier gas and short time duration during which the CO2 is released from the combustion unit, and provides a constant ratio of CO2 to He carrier gas to the ion source. Details of the active control system are presented and results from the testing of this control are provided.
This paper reports on the performance of a new method of sample injection using the High Voltage Engineering Europa (HVEE) SO-110 ion source jointly developed between HVEE and Oxford. In order to use this source, we have devel- oped a new gas handling system which works on the direct injection of carbon dioxide mixed into a continuous flow of helium. Preliminary work has also been carried out on online gas chromatography-accelerator mass spectrometry (GC-AMS). In this application, a GC is directly coupled to the AMS system using a GC-IRMS combustion interface and Nafion™ drier. We show here results for the measurement of natural abundance in separated compounds with good peak separation and pre- cisions of about 10%. This type of system should be ideal for source apportionment studies, biomedical, and other similar work where high precision is not required but where sample sizes are very low.
A data evaluation program was developed at ETH Zurich to meet the requirements of the new compact AMS systems MICADAS and TANDY in addition to the large EN-Tandem accelerator. The program, called “BATS”, is designed to automatically calculate standard and blank corrected results for measured samples. After almost one year of routine operation with the MICADAS C-14 system BATS has proven to be an easy to use data reduction tool that requires minimal user input. Here we present the fundamental principle and the algorithms used in BATS for standard-sized radiocarbon measurements.
The sealed tube zinc reduction method for converting CO 2 to graphite for AMS 14 C measurements was originally developed for rapid production of graphite in biomedical tracer experiments. The method was usually thought to have low precision and a high background. We have modified the zinc reduction method originally outlined in Vogel [J.S. Vogel, Radiocarbon 34 (3) (1992) 344] by carefully con-trolling the amounts of reagents (zinc, titanium hydride and Co or Fe catalyst) and now routinely obtain a precision of 2–3& and a relatively low background of $50,000 14 C years when analyzing for 14 C at the Keck Carbon Cycle AMS facility at UC Irvine. Fraction-ation of carbon isotopes does occur during graphitization and depends on the graphitization yield, which can be affected by the amounts of reagents used and other conditions. The d 13 C of our zinc-reduced graphite is usually lighter by 2–3& than the CO 2 from which it is made, but this is corrected for in our system by simultaneous measurement of 13 C/ 12 C along with 14 C/ 12 C by the spectrometer. This method is suitable for 14 C enriched samples, as well as natural abundance 14 C samples, especially those with modern 14 C contents. With improved precision and background, we believe that many disciplines can benefit from this technique because of its low cost and rapid production of graphite.
The state of the art in accelerator mass spectrometry (AMS) is reviewed. The review is divided in two parts. The first covers the general methodology, followed by its specific elaborations for the commonly measured long-lived isotopes such as 10Be, 14C, 26Al, 36Cl and 129I, as well as other isotopes with emerging applications. The second part considers the very wide spectrum of applications that now employ AMS, and groups these according to research area rather than isotope. The period up until late 1998 is covered, with an emphasis on post-1990 developments and literature.
A novel tabletop AMS system with overall dimensions of only 2.5 x 3 m(2) has been built and tested. The mini radiocarbon dating System (MICADAS) is based on a vacuum insulated acceleration unit that uses a commercially available 200 kV power supply to generate acceleration fields in a tandem configuration. At the high-energy end, ions in charge state 1(+) are selected and interfering molecules of mass 14 amu are destroyed in multiple collisions. The new system is now fully operational. It is the prototype of a new generation of radiocarbon spectrometers which fulfill the requirements for radiocarbon dating applications as well as for the less demanding C-14/C-12 isotopic ratio measurements as needed, e.g. in biomedical applications. A detailed description of the system is given and results of performance tests are discussed. (c) 2007 Elsevier B.V. All rights reserved.
Two catalytic processes have been explored for the preparation of suitable samples for use in 14C measurements on an accelerator mass spectrometer. A heavy hydrocarbon was condensed from C2H2 using AlBr3 as a catalyst. This process had low isotopic fractionation, and the carbon ion beam obtainable was 60–70% that from graphite. In the second process, iron powder was used to produce graphite directly from CO2 and H2 at 600 °C. A sample preparation system using this reaction has been built. The carbon product produces exceptionally intense, long-lived ion beams. The process introduces little 14C background, and has no observed memory effects.
A new graphitisation system, directly coupled to an elemental analyser, has been developed for convenient, fast and efficient sample preparations for radiocarbon measurement by means of accelerator mass spectrometry. We demonstrate an alternative to the cryogenic transport of CO2 into the graphitisation reactors with liquid nitrogen, which is used by others. Instead, the CO2 coming from an EA is absorbed on a single column filled with zeolite. The CO2 can then be easily released by heating the zeolite trap and transferred to the reactor by gas expansion. The system is simple and fully automated for sample combustion and graphitisation.
Radiocarbon accelerator mass spectrometry (AMS) is a high-sensitivity analysis technique which is nowadays widely used in many research fields such as archaeology, geology, environmental and earth sciences. We report on the features of the new high throughput accelerator mass spectrometer at the University of Lecce, Italy. The experimental apparatus is described and its general characteristics are reported in terms of measurement precision, accuracy and achievable background.
A number of operationally defined methods exist for pretreating plant tissues in order to measure C, N, and O isotopes. Because these isotope measurements are used to infer information about environmental conditions that existed at the time of tissue growth, it is important that these pretreatments remove compounds that may have exchanged isotopes or have been synthesized after the original formation of these tissues. In stable isotope studies, many pretreatment methods focus on isolating "cellulose" from the bulk tissue sample because cellulose does not exchange C and O isotopes after original synthesis. We investigated the efficacy of three commonly applied pretreatment methods, the Brendel method and two variants of the Brendel method, the Jayme-Wise method and successive acid/base/acid washes, for use on three tissue types (wood, leaves, roots). We then compared the effect of each method on C and O isotope composition (13C, 14C, 18O), C and N content, and chemical composition of the residue produced (using 13C nuclear magnetic resonance (NMR)). Our results raised concerns over use of the Brendel method as published, as it both added C and N to the sample and left a residue that contains remnant lipids and waxes. Furthermore, this method resulted in 18O values that are enriched relative to the other methods. Modifying the Brendel method by adding a NaOH step (wash) solved many of these problems. We also found that processed residues vary by tissue type. For wood and root tissues, the 13C NMR spectra and the 18O and 13C data showed only small differences between residues for the Jayme-Wise and modified Brendel methods. However, for leaf tissue, 13C NMR data showed that Jayme-Wise pretreatments produced residues that are more chemically similar to cellulose than the other methods. The acid/base/acid washing method generated 13C NMR spectra with incomplete removal of lignin for all tissues tested and both isotopic, and 13C NMR results confirmed that this method should not be used if purified cellulose is desired.
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