• A Beam Profile Monitor for Rare Isotopes in Accelerator Mass Spectrometry: Preliminary Measurements

      Taccetti, F.; Carraresi, L.; Fedi, M. E.; Manetti, M.; Mariani, P.; Tobia, G.; Mandò, P. A. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In accelerator systems, beam lines are generally equipped with diagnostic elements, such as Faraday cups and beam profile monitors (BPM), to optimize beam transport. These diagnostic elements, or at least commercial ones, are designed to only work with continuous beams, and their typical maximum sensitivity is about few tens of pA. Thus, in the case of diagnosis of rare isotope beams in accelerator mass spectrometry (AMS), Faraday cups and BPMs are not suitable on the high-energy side of the tandem accelerator, after energy-mass-charge analysis. For example, in 14C AMS, even for a modern sample, the expected counting rate is a few tens of Hz; in these conditions, a commercial BPM cannot be used. On the other hand, checking the shape and the position of the rare isotope beam hitting the detector can be important in order to better identify signals in the detector itself, thus also helping in reducing the measurement background. This paper presents a prototype BPM especially designed for low-intensity beams. The BPM is based on a multiwire proportional chamber characterized by 2 grids of anode wires, oriented perpendicular to each other in order to measure both the x and the y coordinates of the particle impact point. Details about the design and the electronics of the device are given, and the first test measurements are discussed.
    • A Continuous-Flow Gas Chromatography 14C Accelerator Mass Spectrometry System

      McIntyre, C. P.; Galutschek, E.; Roberts, M. L.; von Reden, K. F.; McNichol, A. P.; Jenkins, W. J. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Gas-accepting ion sources for radiocarbon accelerator mass spectrometry (AMS) have permitted the direct analysis of CO2 gas, eliminating the need to graphitize samples. As a result, a variety of analytical instruments can be interfaced to an AMS system, processing time is decreased, and smaller samples can be analyzed (albeit with lower precision). We have coupled a gas chromatograph to a compact 14C AMS system fitted with a microwave ion source for real-time compound-specific 14C analysis. As an initial test of the system, we have analyzed a sample of fatty acid methyl esters and biodiesel. Peak shape and memory was better then existing systems fitted with a hybrid ion source while precision was comparable. 14C/12C ratios of individual components at natural abundance levels were consistent with those determined by conventional methods. Continuing refinements to the ion source are expected to improve the performance and scope of the instrument.
    • A High-Performance 14C Accelerator Mass Spectrometry System

      Roberts, M. L.; Burton, J. R.; Elder, K. L.; Longworth, B. E.; McIntyre, C. P.; Vo, K. F.; Han, B. X.; Rosenheim, B. E.; Jenkins, W. J.; Galutschek, E.; et al. (Department of Geosciences, The University of Arizona, 2010-01-01)
      A new and unique radiocarbon accelerator mass spectrometry (AMS) facility has been constructed at the Woods Hole Oceanographic Institution. The defining characteristic of the new system is its large-gap optical elements that provide a larger-than-standard beam acceptance. Such a system is ideally suited for high-throughput, high-precision measurements of 14C. Details and performance of the new system are presented.
    • A New 1MV AMS Facility at KIGAM

      Hong, W.; Park, J. H.; Sung, K. S.; Woo, H. J.; Kim, J. K.; Choi, H. W.; Kim, G. D. (Department of Geosciences, The University of Arizona, 2010-01-01)
      A 1MV AMS was installed in KIGAM (Korea Institute of Geoscience and Mineral Resources). After 4 months of installation, the AMS started normal operation from January 2008. This multi-element AMS was developed by HVEE to measure 14C, 10Be, and 26Al. The results of an acceptance test demonstrate that this machine is capable of routine 14C age dating and of measurements of other radioisotopes in terms of accuracy and precision as well as the background level. After installation, an investigation aimed at determining the stable operating conditions was conducted, and background levels were determined to be as low as 10-15 for 14C and 10-14 for 10Be and 26Al.
    • A Nondestructive Prescreening Method for Bone Collagen Content Using Micro-Computed Tomography

      Tripp, J. A.; Squire, M. E.; Hamilton, J.; Hedges, R. E. M. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Isolation of bone collagen for radiocarbon dating is a labor-intensive and time-consuming process that sometimes results in unacceptably low protein recovery. In preliminary studies reported here, micro-computed tomography (microCT), a nondestructive technique that uses X-rays to produce high-resolution three-dimensional images of mineralized materials such as bone, offers promise as a suitable prescreening option for bones of questionable preservation. We have found that the bone volume fraction calculated by the scanner software correlates well with collagen recovery in 4 analyzed bones from Etton, United Kingdom.
    • A Preparative 2D-Chromatography Method for Compound-Specific Radiocarbon Analysis of Dicarboxylic Acids in Aerosols

      Fahrni, S. M.; Ruff, M.; Wacker, L.; Perron, N.; Gäggeler, H. W.; Szidat, S. (Department of Geosciences, The University of Arizona, 2010-01-01)
      There is a great scientific demand for an assessment of the sources and formation processes of atmospheric carbonaceous aerosols since they strongly influence the global radiation balance and affect public health. Much attention in atmospheric studies has been paid to dicarboxylic acids (DCAs) due to their abundance at substantially different sites and their potential influence on cloud formation processes. Nevertheless, sources of oxalic acid (HOOCCOOH) and other DCAs are not well understood yet. In order to quantify contributions of fossil and non-fossil sources, a method for the preparative separation of oxalic acid and other DCAs from aerosols for compound-specific radiocarbon analysis (CSRA) has been developed. This method consists of a water extraction of aerosols collected on quartz-fiber filters followed by 2 consecutive liquid chromatography (LC) steps on different chromatography columns (2D-chromatography). Through the use of aqueous, completely non-organic eluents and single injections into liquid chromatography, low blank levels are achieved with total oxalic acid recoveries of up to 66%. Upon separation, 14C measurements of small samples (containing typically 10-20 g carbon) are conducted at the gas ion source of the 200kV accelerator mass spectrometry facility MICADAS. The method is verified with processed reference materials, artificial mixtures of oxalic acid with typical matrix components, and a standard addition of ambient aerosols. Two exemplary field samples show dominant non-fossil sources of oxalic acid.
    • Age and Growth Rate Dynamics of an Old African Baobab Determined by Radiocarbon Dating

      Patrut, A.; Mayne, D. H.; Vo, K. F.; Lowy, D. A.; Venter, S.; McNichol, A. P.; Roberts, M. L.; Margineanu, D. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In 2008, a large African baobab (Adansonia digitata L.) from Makulu Makete, South Africa, split vertically into 2 sections, revealing a large enclosed cavity. Several wood samples collected from the cavity were processed and radiocarbon dated by accelerator mass spectrometry (AMS) for determining the age and growth rate dynamics of the tree. The 14C date of the oldest sample was found to be of 1016 22 BP, which corresponds to a calibrated age of 1000 15 yr. Thus, the Makulu Makete tree, which eventually collapsed to the ground and died, becomes the second oldest African baobab dated accurately to at least 1000 yr. The conventional growth rate of the trunk, estimated by the radial increase, declined gradually over its life cycle. However, the growth rate expressed more adequately by the cross-sectional area increase and by the volume increase accelerated up to the age of 650 yr and remained almost constant over the past 450 yr.
    • Alternative Explanations for Anomalous 14C Ages on Human Skeletons Associated with the 612 BCE Destruction of Nineveh

      Taylor, R. E.; Beaumont, W. C.; Southon, J.; Stronach, D.; Pickworth, D. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Three factors--contamination, a dietary reservoir effect, and a regional ∆14C anomaly--are considered as possible contributing explanations for an almost 2-century offset between the historically documented age of 612 BCE and the calibrated ages of 9 14C determinations obtained on 3 human skeletons directly associated stratigraphically with an archaeologically--and historically--defined 612 BCE event at the ancient site of Nineveh in northern Mesopotamia (Iraq). We note that on the order of a 1% (~80 yr) offset caused by one or a combination of these 3 factors, or other as yet unidentified additional factor(s), would be sufficient to move the average measured 14C age of these bone samples within the major "warp" in the 14C timescale during the mid-1st millennium BCE. We provide what we believe to be sufficient evidence that contamination is not a major factor in the case of these bone samples. At this time, we lack appropriate data to determine with sufficient rigor the degree to which a dietary reservoir effect may be contributing to the offset. At present, a posited regional ∆14C anomaly does not appear to be supported on the basis of data from several other localities in the Near East of similar age. One purpose of presenting this data set is to solicit comparisons with 14C values obtained on samples from additional, historically well-documented, known-age archaeological contexts for this time period in this and adjacent regions.
    • AMS Radiocarbon Dating of an Ancient Pottery Workshop in Hepu County, China

      Ruan, X.; Guan, Y.; Xiong, Z.; Wu, W.; Wang, H.; Jiang, S.; He, M.; Liu, K.; Terrassi, F.; Capano, M. (Department of Geosciences, The University of Arizona, 2010-01-01)
      An ancient pottery workshop belonging to the Han Dynasty was excavated in Caoxie village, Hepu County. Caoxie village is an important archaeological site in Hepu County, Beihai City, in south China's Guangxi Zhuang Autonomous Region. It is believed that Hepu County was the oldest departure point on the ancient maritime trading route during the Han Dynasty (206 BC to AD 220) due to the ideal natural geographical conditions and the existence of a large number of Han tombs. Radiocarbon measurements on wood and charcoal samples from the Caoxie village site were performed at the Peking University AMS facility (PKU-AMS), Beijing, and the Centre for Isotopic Research for Cultural and Environmental Heritage (CIRCE) at Naples Second University, Italy. Calibrated ages were obtained with code CALIB 5 (Stuiver and Reimer 1993). The results of these measurements are presented and the related chronology is discussed.
    • Archaeological Radiocarbon Dates for Studying the Population History in Eastern Fennoscandia

      Oinonen, M.; Pesonen, P.; Tallavaara, M. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In this work, archaeological radiocarbon data gathered from eastern Fennoscandia have been scrutinized to discuss their suitability for studies of population history. The temporal distribution of the archaeological 14C dates has been analyzed against possible research priorities and sample material deterioration. An outstanding 'Stone Age' maximum has been observed in practically all the displayed temporal date distributions. The pattern remains the same throughout the history of 14C dating in Finland. Due to sample material differences, equal taphonomic corrections based on 14C-dated volcanic deposits cannot account for all the sample degradation effects; therefore, material-dependent correction procedures are suggested.
    • Are Compact AMS Facilities a Competitive Alternative to Larger Tandem Accelerators?

      Suter, M.; Müller, A. M.; Alfimov, V.; Christl, M.; Schulze-König, T.; Kubik, P. W.; Synal, H.-A.; Vockenhuber, C.; Wacker, L. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In the last decade, small and compact accelerator mass spectrometry (AMS) systems became available operating at terminal voltages of 1 MV and below. This new category of instruments has become competitive for radiocarbon detection to larger tandem accelerators and many of these instruments are successfully used for 14C dating or biomedical applications. The AMS group at ETH Zurich has demonstrated that small instruments can be built, which allow measurements also of other radionuclides such as 10Be, 26Al, 129I, and the actinides. 41Ca measurements can be performed with sufficient sensitivity for biomedical applications. A summary of recent developments made at the 500kV Pelletron in Zurich is given and its performance is compared with that of a commercial compact instrument from the company High Voltage Engineering Europe (HVEE) in Amersfoort, the Netherlands, operating at 1MV at CNA in Seville, Spain, as well as with that of larger AMS facilities. It turns out that the ion optics, stripper design, and the detection system are critical for the performance.
    • Atmospheric Fossil Fuel CO2 Measurement Using a Field Unit in a Central European City during the Winter of 2008/09

      Molnár, M.; Haszpra, L.; Svingor, É.; Major, I.; Svetlik, I. (Department of Geosciences, The University of Arizona, 2010-01-01)
      A high-precision atmospheric CO2 monitoring station was developed as a field unit. Within this, an integrating CO2 sampling system was applied to collect samples for radiocarbon measurements. One sampler was installed in the second largest city of Hungary (Debrecen station) and 2 independent 14CO2 sampling lines were installed ~300 km from Debrecen in a rural site at Hegyhtsl station as independent background references, where high-precision atmospheric CO2 mixing ratios have been measured since 1994. Fossil fuel CO2 content in the air of the large Hungarian city of Debrecen was determined during the winter of 2008 using both the measurements of CO2 mixing ratio and 14C content of air. Fossil fuel CO2 was significantly enhanced at Debrecen relative to the clean-air site at Hegyhtsl.
    • Bomb-Pulse Dating of Human Material: Modeling the Influence of Diet

      Georgiadou, E.; Stenström, K. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The atmospheric testing of nuclear weapons during the 1950s and early 1960s produced large amounts of radiocarbon. This 14C bomb pulse provides useful age information in numerous scientific fields, e.g. in geosciences and environmental sciences. Bomb-pulse dating can also be used to date human material (e.g. in forensics and medical science). Bomb-pulse dating relies on precise measurements of the declining 14C concentration in atmospheric carbon dioxide collected at clean-air sites. However, local variations in the 14C specific activity of air and foodstuffs occur, which are caused by natural processes as well as by various human activities. As 14C enters the human body mainly through the diet, variations of 14C concentration in foodstuffs need to be considered. The marine component of the diet is believed to be of particular importance due to the non-equilibrium in 14C specific activity between the atmosphere and aquatic reservoirs during the bomb pulse. This article reviews the 14C concentration in marine foodstuffs during the bomb-pulse era, and models how the marine component in one's diet can affect the precision of bomb-pulse dating of human material.
    • Calibrated 14C Ages of Jomon Sites, NE Japan, and Their Significance

      Omoto, K.; Takeishi, K.; Nishida, S.; Fukui, J. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The traditional archaeological chronology in the Japanese Islands during the Jomon period was essentially based on the relative age given to cord-impressed patterns marked on pottery, as well as the shape of the pottery and the thickness of the cultural layers that were excavated. We aimed to correlate the classical archaeological chronology with calibrated radiocarbon dates, to posit a new chronology for the Jomon period in northeastern Japan. We calibrated 80 accelerator mass spectrometry (AMS) 14C dates from NE Japan and reconstructed a chronological timetable for Hokkaido and the Tohoku District. We collected 43 samples from 5 shellmounds and 2 archaeological sites on Hokkaido Island and 4 shellmounds in the Tohoku District in order to determine the calibrated age of their sites. R values used on Hokkaido Island and the Tohoku District were between 282 and -158 yr and between 0 and -40 yr, respectively. The large R value for the eastern part of Hokkaido Island indicates the influence of the Oyashio Current, while an anomalous R value was obtained from northern Hokkaido Island. These figures show larger apparent R values than those from southwest Japan (Nakamura et al. 2007). The calibrated Jomon period in the investigated area was from 2000 to 200 yr younger than the previous chronology. Calibrated 14C ages of the shellmounds investigated ranged between ~6000 and 3000 yr, correlating to the Early Jomon and Final Jomon periods as indicated by the former archaeological chronology of Honshu Island.
    • Chronology of the Obi-Rakhmat Grotto (Uzbekistan): First Results on the Dating and Problems of the Paleolithic Key Site in Central Asia

      Krivoshapkin, A. I.; Kuzmin, Y. V.; Jull, A. J. T. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The Obi-Rakhmat Grotto is one of the key Paleolithic sites in Central Asia. Archaeological excavations have revealed 22 strata containing archaeological materials. Lithic assemblages from all cultural layers display features similar to both late Middle Paleolithic blade industries and early Upper Paleolithic complexes in Southwest Asia and the Siberian Altai Mountains; this suggests a gradual Middle-to-Upper Paleolithic transition occurred in western Central Asia. Hominid remains found at Obi-Rakhmat (layer 16) show a mixture of archaic and modern traits. Different chronometric methods (radiocarbon, optically stimulated luminescence [OSL], U-series, and electron spin resonance [ESR]) were applied to the site's deposits. It appears that 14C dates are more reliable in terms of correspondence to the general framework of the Paleolithic of Central Asia and neighboring regions, and after critical analysis and the deletion of outliers, the upper part of the site's cultural sequence can be dated between 36,000-41,400 BP (layer 7) and ~48,800 BP (layer 14.1). The U-series dating results are less secure due to the high uranium content and the presence of detritus, which contaminates dated sediments (travertine). The OSL dating gave uniform ages for all cultural succession (~8 m of deposits), and confirms a very rapid sedimentation rate. Results of ESR dating depend greatly on the choice of uptake model. Dates calculated for the early uptake to some extent correspond to 14C data. The linear uptake chosen by Skinner et al. (2007) makes sediments very old (about 55,000-90,000 yr ago), which contradicts 14C dates and does not correspond well to the regional archaeological context.
    • Chronostratigraphic Sequence of Santuario della Madonna Cave (Calabria, Southern Italy): AMS Radiocarbon Data from a New Excavation Area

      Calcagnile, L.; Tinè, V.; Quarta, G.; D'Elia, M.; Fiorentino, G.; Scarciglia, F.; Robustelli, G.; Abate, M.; La Russa, M. F.; Pezzino, A. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The Santuario della Madonna Cave, located near Praia a Mare (Cosenza), along the northwestern coast of Calabria (southern Italy), has an impressive stratigraphy, with occupation phases spanning from the late Paleolithic to the advanced phases of the Middle Bronze Age. Recently, a new excavation area has been opened in the cave from which short-lived vegetal remains were sampled and submitted for accelerator mass spectrometry (AMS) radiocarbon dating. The aim of this study was to define an accurate chronology of the different cultural aspects and to explore the potentialities resulting from application of advanced statistical tools for 14C data analysis in such a context.
    • Developing Ultra Small-Scale Radiocarbon Sample Measurement at the University of Tokyo

      Yokoyama, Y.; Koizumi, M.; Matsuzaki, H.; Miyairi, Y.; Ohkouchi, N. (Department of Geosciences, The University of Arizona, 2010-01-01)
      We have developed accelerator mass spectrometry (AMS) measurement techniques for ultra small-size samples ranging from 0.01 to 0.10 mg C with a new type of MC-SNICS ion source system. We can generate 4 times higher ion beam current intensity for ultra-small samples by optimization of graphite position in the target holder with the new ionizer geometry. CO2 gas graphitized in the newly developed vacuum line is pressed to a depth of 1.5 mm from the front of the target holder. This is much deeper than the previous position at 0.35 mm depth. We measured 12C4+ beam currents generated by small standards and ion beam currents (15-30 mu-A) from the targets in optimized position, lasting 20 min for 0.01 mg C and 65 min for 0.10 mg C. We observed that the measured 14C/12C ratios are unaffected by the difference of ion beam currents ranging from 5 to 30 mu-A, enabling measurement of ultra-small samples with high precision. Examination of the background samples revealed 1.1 mu-g of modern and 1 mu-g of dead carbon contaminations during target graphite preparation. We make corrections for the contamination from both the modern and background components. Reduction of the contamination is necessary for conducting more accurate measurement.
    • Dietary Habits and Freshwater Reservoir Effects in Bones from a Neolithic NE German Cemetery

      Olsen, J.; Heinemeier, J.; Lübke, H.; Lüth, F.; Terberger, T. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Within a project on Stone Age sites of NE Germany, 26 burials from the Ostorf cemetery and some further Neolithic sites have been analyzed by more than 40 accelerator mass spectrometry (AMS) dates. We here present the results of stable isotope and radiocarbon measurements together with reference 14C dates on grave goods from terrestrial animals such as tooth pendants found in 10 of the graves. Age differences between human individuals and their associated grave goods are used to calculate 14C reservoir effects. The resulting substantial reservoir effects have revealed misleadingly high 14C ages of their remains, which originally indicated a surprisingly early occurrence of graves and long-term use of this Neolithic burial site. We demonstrate that in order to 14C date the human bones from Ostorf cemetery, it is of utmost importance to distinguish between terrestrial- and freshwater-influenced diet. The latter may result in significantly higher than marine reservoir ages with apparent 14C ages up to ~800 yr too old. The carbon and nitrogen isotopic composition may provide a basis for or an indicator of necessary corrections of dates on humans where no datable grave goods of terrestrial origin such as tooth pendants or tusks are available. Based on the associated age control animals, there is no evidence that the dated earliest burials occurred any earlier than 3300 BC, in contrast to the original first impression of the grave site (~3800 BC).
    • Dietary Reconstruction and Reservoir Correction of 14C Dates on Bones from Pagan and Early Christian Graves in Iceland

      Sveinbjörnsdóttir, Á. E.; Heinemeier, J.; Arneborg, J.; Lynnerup, N.; Ólafsson, G.; Zoëga, G. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In this study, delta-13C and delta-15N of bone samples from 83 skeletons (79 humans, 2 horses, and 2 dogs) excavated from pagan and early Christian graves from 21 localities in Iceland are used to reconstruct diet of the early settlers in Iceland and possible differences in diet depending on the distance between the excavation site and the seashore. We have radiocarbon dated 47 of these skeletons and used the carbon isotopic composition (delta-13C) to estimate and correct for the marine reservoir effect (the 14C difference between terrestrial and mixed marine organisms). The reservoir-corrected ages lie in the range of AD 780-1270 (68.2% probability). Reservoir age corrections were checked by comparing 14C dates of a horse (terrestrial diet), a dog (highly marine diet), and a human (mixed diet) from the same burial. The range in measured marine protein percentage in individual diet is from about 10% up to 55%, mostly depending on the geographical position (distance from the sea) of the excavation site. We had access to the skeleton (AAR-5908) of the Skálholt bishop Páll Jónsson whose remains are enshrined at the Episcopal residence in Skálholt, southern Iceland. According to written sources, the bishop died in AD 1211. Using our dietary reconstruction, his bones were about 17% marine, which is within the range of human skeletons from the same area, and the reservoir-corrected calibrated 14C age of the skeleton is in accord with the historical date.
    • Dietary Reconstruction of the Okhotsk Culture of Hokkaido, Japan, Based on Nitrogen Composition of Amino Acids: Implications for Correction of 14C Marine Reservoir Effects on Human Bones

      Naito, Y. I.; Chikaraishi, Y.; Ohkouchi, N.; Mukai, H.; Shibata, Y.; Honch, N. V.; Dodo, Y.; Ishida, H.; Amano, T.; Ono, H.; et al. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The relative contribution of marine-derived carbon in the ancient diet is essential for correcting the marine reservoir effect on the radiocarbon age of archaeological human remains. In this study, we evaluated the marine protein consumption of 3 human populations from the Okhotsk culture (about AD 550-1200) in Hokkaido, Japan, based on stable carbon and nitrogen isotopic compositions in bulk bone collagen as well as the nitrogen isotopic composition of glutamic acid and phenylalanine. Despite the similarity of carbon and nitrogen isotopic composition of bulk collagens, nitrogen isotopic composition of their constituent amino acids suggests differences in fur seal contributions among northern Hokkaido (0-24% for Kafukai 1, 0-10% for Hamanaka 2) and eastern Hokkaido (78-80% for Moyoro) populations. It suggests that nitrogen composition of glutamic acid and phenylalanine could provide a detailed picture of ancient human subsistence.