• 14C Wiggle Matching of the 'Floating' Tree-Ring Chronology from the Altai Mountains, Southern Siberia: The Ulkandryk-4 Case Study

      Slusarenko, I. Y.; Christen, J. A.; Orlova, L. A.; Kuzmin, Yaroslav V.; Burr, George S. (Department of Geosciences, The University of Arizona, 2001-01-01)
      The Bayesian approach to calibration of radiocarbon dates was used to wiggle-match the "floating" tree-ring chronology from a Pazyryk culture (Scythian-type complex from Sayan-Altai Mountain system, southern Siberia) burial ground in order to estimate the calendar age of its construction. Seventeen bidecadal tree-ring samples were 14C dated with high precision (+/20-30 yr). The results of wiggle-matching show that the Pazyryk-type burial mounds in the southern Altai Mountains were created in the first part of 3rd century BC.
    • 14C Wiggle-Match Dating in High-Resolution Sea-Level Research

      van de Plassche, O.; Edwards, E. J.; van der Borg, K.; de Jong, A. F. M. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Comparison of two sets of marsh-accumulation records from each of three Connecticut (USA) salt marshes, one based on individually calibrated dates and the other on wiggle-match dating of the same series of dates, shows that wiggle-match dating results in more precise and objective reconstructions of longer-term (10^2-10^3 yr) changes in accumulation rate. On (sub-)century time scales, wiggle-match dating can reveal steps in the calibrated marsh-accumulation envelope as artefacts of the calibration curve, but may also leave real short-term changes in accumulation rate undetected. Wiggle-matches are non-unique, being dependent on the number, quality and distribution of radiocarbon dates in a sequence, how a series of dates is subdivided into groups (representing intervals of uniform accumulation rate), and what is considered a "best match". Samples from the studied salt-marsh deposits required no correction for reservoir effects prior to calibration.
    • A Fresh Water Diet-Derived 14C Reservoir Effect at the Stone Age Sites in the Iron Gates Gorge

      Cook, Gordon T.; Bonsall, C.; Hedges, Robert E. M.; McSweeney, K.; Boronean, V.; Pettitt, Paul B. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Human bones from single inhumation burials and artifacts made from terrestrial mammal (ungulate) bone found in direct association with the skeletons were obtained from the Stone Age site of Schela Cladovei situated just below the Iron Gates Gorge of the River Danube. The results of stable isotope analyses of the human bone collagen are consistent with a heavy dependence on aquatic protein while radiocarbon dating of the samples reveals an offset of 300-500 years between the two sample types, indicating a freshwater reservoir effect in the human bone samples. Since protein consumption is by far the major source of nitrogen in the human diet we have assumed a linear relationship between delta-15N and the level of aquatic protein in each individual's diet and derived a calibration for 14C age offset versus delta-15N which has been applied to a series of results from the site at Lepenski Vir within the gorge. The corrected 14C ages (7310-6720 BP) are now consistent with the previous 14C age measurements made on charcoal from related contexts (7360-6560 BP). In addition, the data indicate a change from a primarily aquatic to a mixed terrestrial/aquatic diet around 7100 BP and this may be argued as supporting a shift from Mesolithic to Neolithic. This study also has wider implications for the accurate dating of human bone samples when the possibility exists of an aquatic component in the dietary protein and strongly implies that delta-15N analysis should be undertaken routinely when dating human bones.
    • An Extraction System to Measure Carbon-14 Terrestrial Ages of Meteorites with a Tandetron AMS at Nagoya University

      Minami, Masayo; Nakamura, Toshio (Department of Geosciences, The University of Arizona, 2001-01-01)
      We have constructed a system to extract carbon from meteorites using a vacuum-tight RF melting method in order to study radiocarbon activities in meteorites. The extraction system was examined using iron standards of known carbon content. The carbon extraction efficiencies and 14C ages of the iron standards by this method were compared with the results obtained previously by our older melting system and a wet oxidation method. Higher collection efficiencies of about 90% for the iron samples of relatively high carbon content were achieved by the new system. The efficiency of extracting a small amount of carbon is also near 90% after improving the extraction procedure. The 14C ages of the iron standards were compared to the ages by the wet method. The results indicate that contamination by modern carbon is negligible in the system. Furthermore, terrestrial 14C ages of two Antarctic meteorites, Y-75102 and ALH-77294, from the Yamato and Allan Hills ice fields, respectively, were determined. The age of Y-75102 is estimated 4.0 +/1.0 ka, and the age of ALH-77294 is 19.5 +/1.2 ka. The 14C ages on the meteorites roughly agree with the literature value. However, further study is needed in improvement on reducing a background value and of complete fusion of a meteorite in the extraction system.
    • Delta-R Correction Values for the Northern Indian Ocean

      Dutta, Koushik; Bhushan, Ravi; Somayajulu, B. L. K. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Apparent marine radiocarbon ages are reported for the northern Indian Ocean region for the pre-nuclear period, based on measurements made in seven mollusk shells collected between 1930 and 1954. The conventional 14C ages of these shells range from 693 +/44 to 434 +/51 BP in the Arabian Sea and 511 +/34 to 408 +/51 BP in the Bay of Bengal. These ages correspond to mean Delta-R correction values of 163 +/30 yr for the northern Arabian Sea, 11 +/35 yr for the eastern Bay of Bengal (Andaman Sea) and 32 +/20 yr for the southern Bay of Bengal. Contrasting reservoir ages for these two basins are most likely due to differences in their thermocline ventilation rates.
    • Dendrochronology and Radiocarbon Dating Methods in Archaeological Studies of Scythian Sites

      Dergachev, Valentin A.; Vasiliev, S. S.; Sementsov, A. A.; Zaitseva, Ganna I.; Chugunov, K. A.; Sljusarenko, I. Ju (Department of Geosciences, The University of Arizona, 2001-01-01)
      We propose a new method of cross-dating the wood samples based on the classical methods of spectral estimation. This method uses the average cross-spectral density as a function of the relative position of the series. Because it is not sensitive to phase shifts in data it is appropriate for cross-dating samples originating from geographically distinct areas. The accuracy of cross dating depends on the integrity of the samples used, and in the case of well-preserved wood samples, the precision of relative age comparison may reach a single year. The method was tested on two dendrochronological series from Scythian barrows of known age in Southern Siberia: the Pazyryk barrows (the Altai Mountains) and the Dogee-Baary -2 burials (Western Sayan Mountains) separated by 450 km. The analysis has shown that the Pazyryk barrow is younger by 80 +/4 yr than the Dogee-Baary -2 burials. This result is in agreement with the new chronology of Scythian-related sites suggested for Southern Siberia and Central Asia.
    • Marine Radiocarbon Reservoir Effect in the Western North Pacific Observed in Archaeological Fauna

      Yoneda, Minoru; Hirota, Masashi; Uchida, Masao; Uzawa, Kazuhiro; Tanaka, Atsushi; Shibata, Yasuyui; Morita, Masatoshi (Department of Geosciences, The University of Arizona, 2001-01-01)
      Faunal remains originating from terrestrial and marine mammals, and belonging to the same archaeological deposits were compared to evaluate the marine radiocarbon reservoir ages around the Hokkaido island, Japan. From five shell middens of different ages from the Jomon period (4900 BP) to the Ainu cultural period (800 BP), 107 animal bone samples were selected for radiocarbon measurements. The apparent age differences between Japanese deer and northern fur seal showed the clear effect of deep-water upwelling in this region. Our data showed relatively stable age differences from 4500 BP to 800 BP, with an estimated Delta-R values around 380 14C yr. Results are consistent with previous estimation based on simulation models and oceanographic properties.
    • New Methods and Critical Aspects in Bayesian Mathematics for 14C Calibration

      Steier, Peter; Rom, Werner; Puchegger, Stephan (Department of Geosciences, The University of Arizona, 2001-01-01)
      The probabilistic radiocarbon calibration approach, which largely has replaced the intercept method in 14C dating, is based on the so-called Bayes' theorem (Bayes 1763). Besides single-sample calibration, Bayesian mathematics also supplies tools for combining 14C results of many samples with independent archaeological information such as typology or stratigraphy (Buck et al. 1996). However, specific assumptions in the "prior probabilities", used to transform the archaeological information into mathematical probability distributions, may bias the results (Steier and Rom 2000). A general technique for guarding against such a bias is "sensitivity analysis", in which a range of possible prior probabilities is tested. Only results that prove robust in this analysis should be used. We demonstrate the impact of this method for an assumed, yet realistic case of stratigraphically ordered samples from the Hallstatt period, i.e. The Early Iron Age in Central Europe.
    • Preliminary Estimate of the Reservoir Age in the Lagoon of Venice

      Zoppi, Ugo; Albani, A.; Ammerman, A. J.; Hua, Quan; Lawson, E. M.; Serandrei Barbero, R. (Department of Geosciences, The University of Arizona, 2001-01-01)
      The Lagoon of Venice was formed about 6000 years ago due to the marine transgression associated with the late Pleistocene sea level rise. Already by the time of the Republic of Venice (727-1797 AD) it was recognized that the future of the city and its many historical buildings was strongly correlated with the future of the lagoon itself. During the centuries many engineering projects such as modification of the fluvial systems, construction of coastal barriers, and dredging of navigation channels were carried out to preserve the lagoonal environment. The present-day lagoon is the result of all these processes and covers an area of 540 km2 with an average depth of 0.6 m. A series of radiocarbon age determinations carried out on material obtained from cores collected in the Lagoon of Venice indicate within the sedimentary units the existence of a number of discontinuities and slumping events due to the highly active lagoonal environment. The evaluation of data obtained from a variety of different materials—both terrestrial and marine—allowed us to determine for the first time the marine reservoir effect in the lagoon of Venice. The discussion includes a comparison with other relevant measurements and a possible explanation to the relatively high reservoir age (1200-1300 yr).
    • Protocol Development for Purification and Characterization of Sub-Fossil Insect Chitin for Stable Isotopic Analysis and Radiocarbon Dating

      Hodgins, Gregory W. L.; Thorpe, J. L.; Coope, G. R.; Hedges, Robert E. M. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Reliable radiocarbon dating depends upon well-defined samples. We have been investigating whether or not reliable 14C dates can be obtained directly from sub-fossil insect cuticle or biochemical fractions derived from it. Initial carbon and nitrogen stable isotope measurements on sub-fossil insect chitin from species with known feeding behaviors found within a single site (St Bees, Cumbria) clustered in a manner reminiscent of trophic level effects seen in terrestrial ecosystems. Although this finding implied some chemical stability, the measurement of CN ratios from the same samples indicated compositional variability. In addition, 14C dates obtained from these same samples were different from dates obtained from plant macrofossils found at the same depth. We have experimented with protocols designed to biochemically reduce chitin to its principle carbohydrate component glucosamine with the aim of using this compound to generate reliable 14C dates. Solvent extractions of sub-fossil chitin were carried out to remove both endogenous and exogenous lipid-soluble materials. Base hydrolysis reactions designed to extract polypeptides retained surprisingly high levels of contaminating amino acids. Proteinase K enzyme treatment had little affect on the level of amino acid contamination. Strong acid hydrolysis reactions designed to depolymerize chitin to glucosamine yielded only 5% glucosamine. Clearly alternative methods of chitin depolymerization must be identified before the purification and 14C dating of glucosamine from sub-fossil chitin becomes practical.
    • Radiocarbon and Dendrochronological Dating of Logboats from Poland

      Pazdur, Anna; Krąpiec, Marek; Michczyński, Adam; Ossowski, Waldemar (Department of Geosciences, The University of Arizona, 2001-01-01)
      The earliest dating of samples taken from logboats found in the area of Poland was done at the Gliwice Radiocarbon Laboratory in the late 1970s and early 1980s. After a 10-year break, the study of their chronology was renewed. The 14C dates (56) include all previously published and new, unpublished results obtained during last several years. Here, we discuss and provide probabilistic interpretation of the calendar age of the dated boats. The calibration of 14C dates was done with the OxCal program for dates less than 300 BP, and with the GdCALIB program for all remaining dates. In distribution of calibrated dates we find a lack of samples between the ages of around 800 BC and 300 AD. This result is surprising and differs from results observed for Central Europe. The remaining age ranges, with high frequency of dates, are in good coincidence with similar periods obtained for Central Europe. Tree-ring dating of oak logboats was carried out on 60 growth sequences, dated against standard chronologies defined for the area of Poland. The results of 14C dating and tree-ring analyses give consistent chronologies.
    • Radiocarbon Dating of Single Compounds Isolated from Pottery Cooking Vessel Residues

      Stott, A. W.; Berstan, R.; Evershed, P.; Hedges, Robert E. M.; Bronk Ramsey, Christopher; Humm, M. J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We have developed and demonstrated a practical methodology for dating specific compounds (and octadecanoic or stearic acid—C18:0—in particular) from the lipid material surviving in archaeological cooking pots. Such compounds may be extracted from about 10 g of cooking potsherd, and, after derivatization, can be purified by gas chromatography. To obtain sufficient material for precise dating repetitive, accumulating, GC separation is necessary. Throughout the 6000-year period studied, and over a variety of site environments within England, dates on C18:0 show no apparent systematic error, but do have a greater variability than can be explained by the errors due to the separation chemistry and measurement process alone. This variability is as yet unexplained. Dates on C16:0 show greater variability and a systematic error of approximately 100-150 years too young, and it is possible that this is due to contamination from the burial environment. Further work should clarify this.
    • Radiocarbon Dating of Wood Using Different Pretreatment Procedures: Application to the Chronology of Rotoehu Ash, New Zealand

      Santos, Guaciara M.; Bird, M. I.; Fifield, L. Keith; Alloway, B. V.; Chappell, J.; Hausladen, P. A.; Arneth, A. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We compare radiocarbon accelerator mass spectrometry (AMS) ages of wood samples subjected to a conventional acid-base-acid pretreatment with stepped combustion (ABA-SC) with results from the same samples subjected to an acid-base-wet oxidation pretreatment with stepped combustion (ABOX-SC) and cellulose extraction with stepped combustion (CE-SC). The ABOX-SC procedure has been shown previously to lead to lower backgrounds for old charcoal samples. Analyses of relatively uncontaminated " 14C-dead" samples of wood suggest that backgrounds of 0.11 +/0.04 pMC are obtainable for both the ABOX-SC and ABA-SC procedures. Where wood is significantly contaminated the ABOX-SC technique provides significantly better decontamination than either the ABA-SC technique or cellulose extraction alone, although CE-SC can produce comparably low backgrounds to the ABOX-SC procedure. We also report the application of the ABOX-SC, ABA-SC and CE-SC procedures to wood samples associated with the chronologically controversial Rotoehu Ash eruption, New Zealand. New 14C-AMS dates from wood sampled from below the Rotoehu Ash span an age range of 43-50 ka BP consistent with recently presented OSL dates of 42-44 ka obtained for palaeosols beneath the ash.
    • Radiocarbon Measurements of Tree Rings from 14 ka Huon Pine

      Lange, Todd; Barbetti, M.; Donahue, Douglas J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We have measured the radiocarbon content of tree rings from a section of Huon pine retrieved from Tasmania. The sample was divided into 39 five-ring sub-samples covering a period of 194 years. Radiocarbon ages of each of these sub-samples was determined by making four measurements of each sub-sample at the Arizona AMS laboratory (Table 1). The resulting 1-sigma precisions are about 0.5%. A comparison of our data with the appropriate curve in INTCAL98 indicates that the calendar age of our sample is close to 14,000 cal BP. Using this age calibration, we have constructed a plot of Delta-14C versus assumed calendar age. This plot shows an essentially constant value over the youngest 125 rings of our sample. Over the oldest 75 yr of the sample, the Delta-14C curve exhibits three fluctuations, the largest of which is about 65 per mil. The time of the peaks in the Huon-pine 14C curve corresponds approximately with the European Bolling/Allerod climatic event. Work is in progress to extend the data 100 yr more toward older ages.
    • Radiocarbon Reservoir Correction Ages in the Peter the Great Gulf, Sea of Japan, and Eastern Coast of the Kunashir, Southern Kuriles (Northwestern Pacific)

      Kuzmin, Yaroslav V.; Burr, George S.; Jull, A. J. Timothy (Department of Geosciences, The University of Arizona, 2001-01-01)
      The radiocarbon reservoir age correction values (R) for the Russian Far East are estimated as 370 +/26 yr for the northwestern Sea of Japan, and 711 +/46 yr for the southern Kurile Islands.
    • Searching Solar Periodicities in the Late Glacial Record of Atmospheric Radiocarbon

      Goslar, Tomasz; Tisnérat,-Laborde, Nadine; Paterne, Martine (Department of Geosciences, The University of Arizona, 2001-01-01)
      Accelerator mass spectrometry radiocarbon (AMS 14C) dating of the late glacial section of laminated sediments from Lake Gościąż and Lake Perespilno, Poland, performed with time resolution of 20-30 years suggests quasi-periodic oscillations of Delta-14C. The regularity of oscillations has been checked by the Maximum Entropy and Fast Fourier Transform methods (MEM and FFT), which revealed peaks at 200 and 230 yr. These periods are similar to those found in the high-precision Holocene Delta-14C record, and attributed to the changing sun. The analytical assessment of the significance of the FFT and MEM peaks is problematic because of non-uniform spacing and various uncertainties in the input data. The significance of the peaks has therefore been studied by the Monte-Carlo method. Because the original data were approximated with a spline function, the amplitude of the MEM and FFT peaks depends on the stiffness of the spline, which is strongly related to the "real" uncertainty of 14C ages. The Monte-Carlo experiments demonstrate that the significance levels of the MEM and FFT peaks also depend on the spline stiffness. Therefore, the existence of solar 14C variations in the Late Glacial remains an open question.
    • Seasonal Fluctuation of Stable Carbon Isotopic Composition in Japanese Cypress Tree Rings from the Last Glacial Period—Possibility of Paleoenvironment Reconstruction

      Takahashi, Hiroshi Aoki; Yonenobu, Hitoshi; Nakamura, Toshio; Wada, Hideki (Department of Geosciences, The University of Arizona, 2001-01-01)
      Seasonal variations of delta-13C were analyzed for two Japanese cypress trees (Chamaecyparis obtusa), one buried and one living. Both trees were different in age but sampled in areas geographically close to each other in central Japan. A buried cypress with 394 annual rings was excavated from Old Fuji mudflow, the last glacial strata of the dormant Mt. Fuji volcano. The accelerator mass spectrometry (AMS) radiocarbon date of this glacial sample was 18,600 +/120 BP (NUTA-4884). A living tree stem, which has 192 rings, was cut from the Izu Peninsula in 1986. In order to measure the seasonal delta-13C fluctuation, the tree rings were divided equally into three earlywood and one or two latewood consecutive sections. The delta-13C value within an annual ring generally increased from the first to the third or fourth sections then decreased in the last section. This pattern of the variation was similar in the glacial and modern samples. The delta-13C value within an annual ring seems to be controlled by environmental factors (not plant physiological ones), since there was no isotopic shift in the seasonal delta-13C variation at the earlywood-latewood boundary, which was controlled by plant physiology. The result suggests the potential to reconstruct the paleoenvironment within a year using the seasonal delta-13C variation, though site-specific conditions such as soil characteristics would also affect to its fluctuation.
    • Solar Activity and Regional Climate

      Ogurtsov, M. G.; Kocharov, Grant E.; Lindholm, M.; Eronen, M.; Nagovitsyn, Yu A. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We performed a statistical analysis of the data on summer temperature anomalies in northern Fennoscandia (8-1995 AD) and found that a 70-130-yr cycle is present in this series during most of the time period. A comparison of the reconstructed northern Fennoscandia temperature with different indicators of solar activity (Wolf numbers, the length of solar Schwabe cycle, extended bi-decadal radiocarbon series, and data on sunspots observed by naked eye) shows that the more probable cause of the periodicity is the modulation of regional northern Fennoscandia climate by the long-term solar cycle of Gleissberg. The effect of this century-scale solar modulation of the global Northern Hemisphere temperature is weaker.
    • Transition Dating' – A Heuristic Mathematical Approach to the Collation of Radiocarbon Dates from Stratified Sequences

      Sharon, Ilan (Department of Geosciences, The University of Arizona, 2001-01-01)
      A heuristic approach, nicknamed "transition dating," was used to date sequences of early Iron Age contexts using a series of 14C determinations. The basic principles of transition dating are simple and intuitive: 1) attempt to date transitions between periods, phases, etc. Rather than the phases themselves, and 2) the most plausible date for that transition is one that is later than the dates from contexts preceding it, and is still earlier than the dates succeeding it. Hypotheses regarding the actual date of each transition may be evaluated using an appropriate loss function. These loss functions can also be adjusted or weighted by the user to account differentially for the various factors causing the distortion or "fuzz" in the dates.
    • 'Wiggle Matching’ Radiocarbon Dates

      Bronk Ramsey, Christopher; van der Plicht, Johannes; Weninger, B. (Department of Geosciences, The University of Arizona, 2001-01-01)
      This paper covers three different methods of matching radiocarbon dates to the "wiggles" of the calibration curve in those situations where the age difference between the 14C dates is known. These methods are most often applied to tree-ring sequences. The simplest approach is to use a classical Chi-squared fit of the 14C data to the 14C curve. This gives the calendar date where the data fit best and allows tests of how good the fit is. The only drawback of this method is that it is difficult to ascertain the uncertainty in the date found in this way. An extension of this technique uses a Monte-Carlo simulation to sample possible 14C concentrations consistent with the measurement made and for each of these possibilities performs a Chi-squared fit. This method yields a distribution of values in the calendrical time-scale, from which the overall dating uncertainty can be derived. A third, rather different approach, based on Bayesian statistics, calculates the relative likelihood of each possible calendar year fit. This can then be used to calculate a range of most likely dates in a similar way to the probability method of 14C calibration. The theories underlying all three methods are discussed in this paper and a comparison made for the fitting of specific model sequences. All three methods are found to give consistent results and the application of any one of them depends on the nature of the scientific question being addressed.