• Radiocarbon and Stable Isotope Evidence of Dietary Change from the Mesolithic to the Middle Ages in the Iron Gates: New Results from Lepenski Vir

      Bonsall, C.; Cook, G. T.; Hedges, R. E. M.; Higham, T. F. G.; Pickard, C.; Radovanović, I. (Department of Geosciences, The University of Arizona, 2004-01-01)
      A previous radiocarbon dating and stable isotope study of directly associated ungulate and human bone samples from Late Mesolithic burials at Schela Cladovei in Romania established that there is a freshwater reservoir effect of approximately 500 yr in the Iron Gates reach of the Danube River valley in southeast Europe. Using the d15N values as an indicator of the percentage of freshwater protein in the human diet, the 14C data for 24 skeletons from the site of Lepenski Vir were corrected for this reservoir effect. The results of the paired 14C and stable isotope measurements provide evidence of substantial dietary change over the period from about 9000 BP to about 300 BP. The data from the Early Mesolithic to the Chalcolithic are consistent with a 2-component dietary system, where the linear plot of isotopic values reflects mixing between the 2 end-members to differing degrees. Typically, the individuals of Mesolithic age have much heavier d15N signals and slightly heavier d13C, while individuals of Early Neolithic and Chalcolithic age have lighter d15N and d13C values. Contrary to our earlier suggestion, there is no evidence of a substantial population that had a transitional diet midway between those that were characteristic of the Mesolithic and Neolithic. However, several individuals with Final Mesolithic 14C ages show d15N and d13C values that are similar to the Neolithic dietary pattern. Provisionally, these are interpreted either as incomers who originated in early farming communities outside the Iron Gates region or as indigenous individuals representing the earliest Neolithic of the Iron Gates. The results from Roman and Medieval age burials show a deviation from the linear function, suggesting the presence of a new major dietary component containing isotopically heavier carbon. This is interpreted as a consequence of the introduction of millet into the human food chain.
    • Pushing the Precision Limit of 14C AMS

      Steier, Peter; Dellinger, Franz; Kutschera, Walter; Priller, Alfred; Rom, Werner; |Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2004-01-01)
      High precision for radiocarbon cannot be reached without profound insight into the various sources of uncertainty which only can be obtained from systematic investigations. In this paper, we present a whole series of investigations where in some cases 16O:17O:18O served as a substitute for 12C:13C:14C. This circumvents the disadvantages of event counting, providing more precise results in a much shorter time. As expected, not a single effect but a combination of many effects of similar importance were found to be limiting the precision. We will discuss the influence of machine tuning and stability, isotope fractionation, beam current, space charge effects, sputter target geometry, and cratering. Refined measurement and data evaluation procedures allow one to overcome several of these limitations. Systematic measurements on FIRI-D wood show that a measurement precision of +/20 14C yr (1 sigma) can be achieved for single-sputter targets.
    • Preparation of Graphite Targets from Small Marine Samples for AMS Radiocarbon Measurements

      Kwong, Laval Liong Wee; Povinec, Pavel P.; Jull, A. J. Timothy (Department of Geosciences, The University of Arizona, 2004-01-01)
      A vacuum sample processing line was set up and methods were developed for the determination of radiocarbon in small-volume seawater and biota samples. Seawater samples (500 mL per borosilicate glass bottle and poisoned with HgCl2) were acidified with 5 mL concentrated hydrochloric acid. Pure N2 was used as a carrier gas to strip CO2 from the samples for 10 min in a circulation mode. After purification through several water traps, the CO2 was isolated cryogenically. Using Na2CO3 standard solutions, recovery yields were calculated superior to 95 +/5%. Freeze-dried marine biota samples were thoroughly mixed with Cu(II)O and combusted at 900 degrees C. The CO2 was purified by passing through Ag wool and Cu granules at 450 degrees C before reduction to graphite. Finally, graphite was synthesized using Zn dust heated to 450 degrees C in the presence of an Fe catalyst at 550 degrees C. Although this method takes about 8 hr (synthesis done overnight), the advantage is that no water vapor by-product is formed to hinder the reaction. The graphite yields, measured both by gravimetric methods and by pressure readings, were 95 +/5%. Accelerator mass spectrometry (AMS) measurements were carried out at the NSF-Arizona AMS Facility. Results for water samples from the northwest Pacific Ocean are reported which are in agreement with data reported elsewhere.
    • Problems Associated with the AMS Dating of Small Bone Samples: The Question of the Arrival of Polynesian Rats to New Zealand

      Higham, T. F. G.; Hedges, R. E. M.; Anderson, A. J.; Ramsey, C. Bronk; Fankhauser, B. (Department of Geosciences, The University of Arizona, 2004-01-01)
      We have AMS dated samples of Pacific rat (Rattus exulans) bone collagen and filtered gelatin samples from the prehistoric site of Shag River Mouth, New Zealand. The age of occupation of this site has previously been determined based on 50 radiocarbon measurements. The site dates to the late Archaic phase of southern New Zealand prehistory (about 650-500 BP; 14th-15th century AD). The results of rat bones which we have dated produce a range in ages, from about 980-480 BP, a difference we attribute to a combination of effects. Pretreatment appears to be an important variable, with results showing differences in 14C age between the progressive collagen and filtered gelatin chemical treatment stages. Amino acid profiles suggest there is a proteinaceous but non-collagenous contaminant which is removed by the more rigorous pretreatment. Stable isotopes vary between pretreatments, supporting the removal of a contaminant, or contaminants. Variation in d15N values imply a range in uptake of dietary protein, and might suggest a potential influence from the local aquatic environment or the consumption of marine-derived protein. Rats are opportunistic, omnivorous mammals, and, therefore, obtain carbon from a variety of reservoirs and so we ought to expect that in environments where there is a variety of reservoirs, these will be exploited. Taken together, the results show that rat bone AMS 14C determinations vary in comparison with the established age of the site, but are in notably better agreement with non-collagenous data than in previously published determinations (Anderson 1996).
    • Preliminary Results for the Extraction and Measurement of Cosmogenic in Situ 14C from Quartz

      Naysmith, P.; Cook, G. T.; Phillips, W. M.; Lifton, N. A.; Anderson, R. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Radiocarbon is produced within minerals at the earth's surface (in situ production) by a number of spallation reactions. Its relatively short half-life of 5730 yr provides us with a unique cosmogenic nuclide tool for the measurement of rapid erosion rates (>10^-3 cm yr-1) and events occurring over the past 25 kyr. At SUERC, we have designed and built a vacuum system to extract 14C from quartz which is based on a system developed at the University of Arizona. This system uses resistance heating of samples to a temperature of approximately 1100 degrees C in the presence of lithium metaborate (LiBO2) to dissolve the quartz and liberate any carbon present. During extraction, the carbon is oxidized to CO2 in an O2atmosphere so that it may be collected cryogenically. The CO2 is subsequently purified and converted to graphite for accelerator mass spectrometry (AMS) measurement. One of the biggest problems in measuring in situ 14C is establishing a low and reproducible system blank and efficient extraction of the in situ 14C component. Here, we present initial data for 14C-free CO2, derived from geological carbonate and added to the vacuum system to determine the system blank. Shielded quartz samples (which should be 14C free) and a surface quartz sample routinely analyzed at the University of Arizona were also analyzed at SUERC, and the data compared with values derived from the University of Arizona system.
    • Preliminary 14C Dates on Bulk Soil Organic Matter from the Black Creek Megafauna Fossil Site, Rocky River, Kangaroo Island, South Australia

      Forbes, Matt; Bestland, Erick; Wells, Rod (Department of Geosciences, The University of Arizona, 2004-01-01)
      Radiocarbon age determinations and stratigraphy suggest that the deposits in Black Creek Swamp on Kangaroo Island record 3 phases of deposition and associated soil development which spanned at least the last 20,000 yr. Four new 14C age determinations on bulk soil organic matter and their stratigraphic context are presented in this paper. Three of these age determinations (FP6: 15,687 +/110 BP [WK11487]; FP7: 16,326 +/385 BP [WK11488]; and FP8: 17,618 +/447 BP [WK11489]), are from the organic-rich fossil layer located 45-75 cm below the current floodplain surface. The fourth, a much younger date, FP5: 5589 +/259 BP (WK11486), was obtained from the base of the overlying modern soil. The dates for the fossil layer increase systematically with depth and correlate well with 5 previous 14C dates (Hope et al., unpublished), ranging between 15,040 +/120 BP and 19,000 +/310 BP. This suggests that the data set represents a possible minimum age of the bulk organic matter, and considering the high organic matter contents of approximately 8%, has implications for the age of the megafauna buried in this layer. The overlying modern soil, with its much younger date, contains lower levels of organic matter (3-7%) and gastropods not seen in the fossil layer. This suggests a substantial change in environmental conditions probably due to an alteration in the floodplain drainage conditions. This chronological and sedimentological discontinuity indicates that 2 distinct depositional regimes existed and were separated by up to 10,000 14C yr. A calcareous, sandy silt deposit underlying the fossil layer is a calcarenite deposit with low total organic content and is considered the base of the section; it suggests a third separate depositional episode. As such, the Black Creek Swamp in the southwest corner of Kangaroo Island formed intermittently over at least the last 20,000 yr during 3 distinct depositional phases, one of which was the formation of the fossil-laden, organic-rich floodplain surface, which has a possible minimum age of approximately 15,000 to 19,000 BP.
    • Pathways for Escape of Magmatic Carbon Dioxide to Soil Air at Unzen Volcano, SW Japan

      Takahashi, Hiroshi A.; Kazahaya, Kohei; Shinohara, Hiroshi; Nakamura, Toshio (Department of Geosciences, The University of Arizona, 2004-01-01)
      Estimation of the magmatic contribution to soil air at Unzen Volcano, SW Japan, was carried out using carbon isotopes, both 14C and 13C, and a mixing model of isotopic mass balance in order to assess the spatial variation of magmatic influence from the volcano. The advantage of using soil air samples is that a wide range of gas sampling sites can be selected. Magmatic CO2 contributed mostly in the eastern region from Unzen Volcano. The high magmatic contribution to soil air appeared along the Akamatsudani fault zone located southeast of the volcano. Our observations across the fault also showed remarkable peaks of CO2 concentration and delta-13C values, suggesting that magmatic fluid comes up along the fracture zone as for the normal fault system of the graben.
    • Neolithic Massacres: Local Skirmishes or General Warfare in Europe?

      Stadler, Peter; Häußer, Annemarie; Kutschera, Walter; Steier, Peter; Teschler-Nicola, Maria; Wahl, Joachim; Windl, Helmut J. (Department of Geosciences, The University of Arizona, 2004-01-01)
      The Neolithic site of Schletz in Lower Austria comprises a fortified settlement from the end of the Linearbandkeramik (LBK) culture. Large numbers of human bones were found at the base of the fortification ditches, and many of the excavated bones and skulls showed evidence of trauma which most likely originates from violence. This remarkable deposit of human remains has been considered evidence for an abrupt end to the Early Neolithic settlement at Schletz. In order to investigate this interpretation, radiocarbon accelerator mass spectrometry (AMS) measurements of human bone samples from this site were performed at VERA. The X2 test of the results from specimens with clearly identified lesions suggests that these may be contemporaneous. Further, it may be concluded that all individuals with evidence of trauma from Schletz were probably the victims of a single event: a massacre at the end of the LBK. Similar evidence is found at Early Neolithic sites at Talheim and Herxheim in the western part of Germany. Analysis of the 14C ages of bones from both sites suggests that the Talheim event may have been coeval with the massacre of Schletz, whereas an event at Herxheim might have happened some time earlier. For Herxheim, the massacre theory is still under discussion, and a change in the burial rite is also considered as an alternative interpretation.
    • Measurement of Low 14C Activities in a Liquid Scintillation Counter in the Zagreb Radiocarbon Laboratory

      Horvatinčić, Nada; Barešić, Jadranka; Krajcar Bronić, Ines; Obelić, Bogomil (Department of Geosciences, The University of Arizona, 2004-01-01)
      Two methods of chemical preparation of radiocarbon samples are implemented in the Zagreb Radiocarbon Laboratory for measurement by a new liquid scintillation counter (LSC), Quantulus 1220(TM): a CO2 absorption method (LSC-A) and a benzene synthesis method (LSC-B). For samples prepared by both methods, the optimal counting windows for measurement in LSC were determined. The total efficiency of LSC-A is 65% and that of the LSC-B is 83%, while the corresponding 14C dating limits are 31,800 yr and 52, 160 yr, respectively. 14C activities measured by the LSC-A and LSC-B methods were compared with those measured by the gas proportional counter (GPC) method (efficiency 75%, 14C dating limit 37,500 yr). The results obtained by the LSC-A method have larger errors than those measured by the GPC method, but LSC-A is quick, inexpensive, simple, and requires less carbon than the GPC method. Thus, LSC-A is suitable for 14C measurements of geological, hydrological, and environmental samples. On the other hand, the results obtained by the LSC-B method give smaller errors and a larger 14C dating range. Therefore, LSC-B is more suitable for 14C dating of archaeological samples.
    • Magnesium Perchlorate as an Alternative Water Trap in AMS Graphite Sample Preparation: A Report on Sample Preparation at KCCAMS at the University of California, Irvine

      Santos, G. M.; Southon, J. R.; Druffel-Rodriguez, K. C.; Griffin, S.; Mazon, M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      We present a brief discussion of sample preparation procedures at the Keck Carbon Cycle Accelerator Mass Spectrometer (KCCAMS), University of California, Irvine, and a systematic investigation of the use of Mg(ClO4)2 as an absorptive water trap, replacing the standard dry ice/ethanol cold finger in graphite sample preparation. We compare high-precision AMS measurement results from oxalic acid I and USGS coal samples using Mg(ClO4)2 under different conditions. The results obtained were also compared with those achieved using the conventional water removal technique. Final results demonstrate that the use of Mg(ClO4)2 as an alternative water trap seems very convenient and reliable, provided the Mg(ClO4)2 is replaced frequently.
    • Lugovskoe, Western Siberia: A Possible Extra-Arctic Mammoth Refugium at the End of the Late Glacial

      Orlova, Lyobov A.; Zenin, Vasily N.; Stuart, Anthony J.; Higham, Thomas F. G.; Grootes, Pieter M.; Leshchinsky, Sergei V.; Kuzmin, Yaroslav V.; Pavlov, Aleksander F.; Maschenko, Evgeny N. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Eleven woolly mammoth bone samples from Lugovskoe (central West Siberian Plain, Russia) were radiocarbon dated in 3 laboratories: Institute of Geology, Novosibirsk; Oxford University, Oxford; and Christian Albrechts University, Kiel. Each laboratory used its own protocol for collagen extraction. Parallel dating was carried out on 3 samples in Novosibirsk and Oxford. Two results are in good agreement. However, there is a major discrepancy between 2 dates obtained for the third sample. The dates obtained so far on the Lugovskoe mammoths range from about 18,250 BP to about 10,210 BP. The Lugovskoe results thus far confirm the possibility of woolly mammoth survival south of Arctic Siberia in the Late Glacial after about 12,000 BP, which has important implications for interpreting the process of mammoth extinction. The site has also produced the first reliable traces of human occupation from central Western Siberia at the Late Glacial, including unique direct evidence of mammoth hunting.
    • Ion Source Development at KCCAMS, University of California, Irvine

      Southon, J. R.; Santos, G. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      The Keck Carbon Cycle accelerator mass spectrometry facility at the University of California, Irvine, operates a National Electronics Corporation 40-sample MC-SNICS ion source. We describe modifications that have increased beam current output, improved reliability, and made the source easier to service.
    • Initial Results with Low Energy Single Stage AMS

      Schroeder, J. B.; Hauser, T. M.; Norton, G. A.; Klody, G. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      The National Electrostatics Corporation has built and tested a prototype low energy, open-air, single stage carbon accelerator mass spectrometry (AMS) system (patent pending). The configuration tested has a standard 40-sample, multicathode SNICS source on a 300-kV deck. The beam is mass analyzed before acceleration to a gas stripper located at ground. The 14C+ ions are separated from 13C+ and super 12C+ arising from the molecular breakup by a 90 degrees analyzing magnet immediately after the gas stripper which acts as a molecular dissociator. The 14C+ beam passes through an electrostatic spherical analyzer before entering the particle detector. The observed 14C/12C precision is better than 5 per mil with a sensitivity of better than 0.05 dpm/gmC. A first single stage AMS system has been ordered. The configuration of this system will be discussed.
    • Improvements to the Pretreatment of Bone at Oxford

      Bronk Ramsey, Christopher; Higham, Thomas; Bowles, Angela; Hedges, Robert (Department of Geosciences, The University of Arizona, 2004-01-01)
      Bone is one of the most widely used materials for dating archaeological activity. It is also relatively difficult to pretreat effectively and new methods are an area of active research. The purpose of the chemical pretreatment of bone is to remove contaminants present from burial and to do so in a way which does not add any additional laboratory contaminant. To some extent, these two aims must be balanced since, on the whole, the more complex the procedure and the more steps included, the greater the chance for contamination. At the Oxford Radiocarbon Accelerator Unit (ORAU), the method used is a continuous-flow or manual acid/base/acid (ABA) treatment followed by gelatinization and ultrafiltration (based on Brown et al. [1988]; documented in Bronk Ramsey et al. [2000]). We find this overall method is very effective at removing more recent contamination in old bones. However, two aspects of the method have recently been improved and are reported here: the redesign of ORAU's continuous flow pretreatment and a new protocol in our pretreatment ultrafiltration stage.
    • Fast and Accurate Sequential Injection AMS with Gated Faraday Cup Current Measurement

      Klein, M.; Mous, D. J. W.; Gottdang, A. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Sequential injection or bouncing has a number of properties which can lead to a reduction of the analysis accuracy if no appropriate measures are taken. A special injection system has been developed in order to eliminate these shortcomings. The influence of source glitches or instabilities on the measured isotopic ratio is substantially reduced by a high cycling frequency. A fast beam-blanking unit guarantees the needed accuracy of the injection periods. Background currents are avoided by synchronizing the current measurement for the stable isotopes with their injection periods. To achieve the required speed and precision of the gated measurement, new instrumentation was developed. The elimination of background contributions allows an efficiency for radiocarbon counting as high as 95% at a cycling frequency of 100 Hz.
    • Extraction and AMS Dadiocarbon Dating of Pollen from Lake Baikal sediments

      Piotrowska, Natalia; Bluszcz, Andrzej; Demske, Dieter; Granoszewski, Wojciech; Heumann, Georg (Department of Geosciences, The University of Arizona, 2004-01-01)
      This work focuses on the preparation and dating of sporomorph (pollen and spores) concentrates of high purity. Three sediment cores recovered from Lake Baikal within the EU-Project CONTINENT were subjected to palynological analyses and accelerator mass spectrometry (AMS) radiocarbon dating. Laboratory processing of concentrates was aimed at the removal of non-sporomorph organic matter by means of chemical treatment, micro-sieving, and heavy liquid separation. The obtained concentrates were checked under the microscope and sample purity was estimated on the basis of particle counts. The results of AMS 14C dating show differences in the sedimentation rate among 3 sites of Lake Baikal.
    • Direct Coupling of an Elemental Analyzer and a Hybrid Ion Source for AMS Measurements

      Uhl, Thomas; Kretschmer, Wolfgang; Luppold, Wolfgang; Scharf, Andreas (Department of Geosciences, The University of Arizona, 2004-01-01)
      The requests to measure many samples, and samples with very low carbon masses, make it necessary to develop new techniques in sample handling to accelerate sample preparation and to eliminate carbon contamination. Our 40 MC-SNICS was recently modified to a hybrid ion source. To run the hybrid ion source with a gas parameter, settings were studied and a gas handling system for the direct coupling of an elemental analyzer and a gas ion source was developed.
    • Development of a Combustion System for Liquid or Gas Samples

      Park, J. H.; Lee, C. S. (Department of Geosciences, The University of Arizona, 2004-01-01)
      While it is customary to use solid samples for measuring the 14C/12C ratio, it is sometimes necessary to handle liquid or gas samples. Motivated by a scientific purpose to count radiocarbon yields in deuterated acetone irradiated with energetic neutrons, we developed a new combustion system to treat liquid or gas samples. In contrast with the typical combustion system using CuO for solid samples, the new combustion system uses high-purity O2 (99.999%) gas. As an initial investigation, we combusted deuterated acetone (acetone-d6, certified 100.0 atm % D) to make CO2 under the ambient O2 pressure. The resulting CO2 gas then went through the reduction process to form graphite for further accelerator mass spectrometry (AMS) measurement.
    • Dating of Total Soil Organic Matter Used in Kurgan Studies

      Molnár, M.; Joó, K.; Barczi, A.; Szánto, Z.; Futó, I.; Palcsu, L.; Rinyu, L. (Department of Geosciences, The University of Arizona, 2004-01-01)
      We investigated Csipo-halom, one of the kurgans that served as a burial place in the Hortobágy area of the Hungarian Great Plain. For pedological description and other studies of the protected mound and its surroundings, only a few monitoring drillings were permitted to get soil samples. On the basis of morphological and visual studies, the structure and layers of the mound were reconstructed. The Laboratory of Environmental Studies of the Institute of Nuclear Research at the Hungarian Academy of Sciences (INR/HAS) performed radiocarbon measurements of soil samples, applying a bulk combustion pretreatment method. The measured 14C ages of soil samples from reference points, such as the top layer of the mound, the center of mound body, the base layer of the mound, the near surroundings, and the distant surroundings, are in good agreement with the preliminary archaeological concept for this field and give substantial information about the rate of soil generation processes in this area.
    • Dating the Volcanic Eruption at Thera

      Bronk Ramsey, Christopher; Manning, Sturt W.; Galimberti, Mariagrazia (Department of Geosciences, The University of Arizona, 2004-01-01)
      The eruption of the volcano at Thera (Santorini) in the Aegean Sea undoubtedly had a profound influence on the civilizations of the surrounding region. The date of the eruption has been a subject of much controversy because it must be linked into the established and intricate archaeological phasings of both the prehistoric Aegean and the wider east Mediterranean. Radiocarbon dating of material from the volcanic destruction layer itself can provide some evidence for the date of the eruption, but because of the shape of the calibration curve for the relevant period, the value of such dates relies on there being no biases in the data sets. However, by dating the material from phases earlier and later than the eruption, some of the problems of the calibration data set can be circumvented and the chronology for the region can be resolved with more certainty. In this paper, we draw together the evidence we have accumulated so far, including new data on the destruction layer itself and for the preceding cultural horizon at Thera, and from associated layers at Miletos in western Turkey. Using Bayesian models to synthesize the data and to identify outliers, we conclude from the most reliable 14C evidence (and using the INTCAL98 calibration data set) that the eruption of Thera occurred between 1663 and 1599 BC.