• From the Guest Editors

      Bronk Ramsey, Christopher; Higham, Thomas F. G. (Department of Geosciences, The University of Arizona, 2007-01-01)
    • The Early Medieval Origin of Perth, Scotland

      Hall, D. W.; Cook, G. T.; Hall, M. A.; Muir, G. P. K.; Hamilton, D.; Scott, E. M. (Department of Geosciences, The University of Arizona, 2007-01-01)
      The radiocarbon results (and Bayesian modeling) of 15 samples of carbonized food residues removed from the external surface of rim sherds of cooking pots indicate that shellyware pottery first appeared in Perth, Scotland, around cal AD 910-1020 (95% probability) and that it had disappeared by cal AD 1020-1140 (95% probability). Previously, it had been suggested that this pottery could not date to before AD 1150. These data, together with 14C analyses carried out on leather artifacts and a sample of wattle from a ditch lining, also demonstrate that there was occupation in Perth about 100 yr or more prior to the granting of royal burgh status to Perth in the 1120s.
    • The Catacomb Cultures of the North-West Caspian Steppe: 14C Chronology, Reservoir Effect, and Paleodiet

      Shishlina, N. I.; Van der Plicht, J.; Hedges, R. M.; Zazovskaya, E. P.; Sevastyanov, V. S.; Chichagova, O. A. (Department of Geosciences, The University of Arizona, 2007-01-01)
      For the Bronze Age Catacomb cultures of the North-West Caspian steppe area in Russia, there is a conflict between the traditional relative archaeological chronology and the chronology based on radiocarbon dates. We show that this conflict can be explained largely by the fact that most dates have been obtained on human bone material and are subject to 14C reservoir effects. This was demonstrated by comparing paired 14C dates derived from human and terrestrial herbivore bone collagen. In addition, values of stable isotope ratios (d13C and d15N) and analysis of food remains from vessels and the stomach contents of buried individuals indicate that a large part of the diet of these cultures consisted of fish and mollusks, and we conclude that this is the source of the reservoir effect.
    • Timescale for Climatic Events of Subboreal/Subatlantic Transition Recorded at the Valakupiai Site, Lithuania

      Pawlyta, Jacek; Gaigalas, Algirdas; Michczyński, Adam; Pazdur, Anna; Sanko, Aleksander (Department of Geosciences, The University of Arizona, 2007-01-01)
      Oxbow lake deposits of the Neris River at the Valakupiai site in Vilnius (Lithuania) have been studied by different methods including radiocarbon dating. A timescale was attained for the development of the oxbow lake and climatic events recorded in the sediments. 14C dates obtained for 24 samples cover the range 990-6500 BP (AD 580 to 5600 BC). Medieval human activity was found in the upper part of the sediments. Mollusk fauna found in the basal part of the terrace indicate contact between people living in the Baltic and the Black Sea basins. Mean rates were calculated for erosion of the river and for accumulation during the formation of the first terrace.
    • Investigation into Background Levels of Small Organic Samples at the NERC Radiocarbon Laboratory

      Ertunç, Tanya; Xu, Sheng; Bryant, Charlotte L.; Currie, Margaret; Freeman, Stewart P. H. T.; Maden, Colin; Murray, Callum (Department of Geosciences, The University of Arizona, 2007-01-01)
      Recent progress in preparation/combustion of submilligram organic samples at our laboratories is presented. Routine methods had to be modified/refined to achieve acceptable and consistent procedural blanks for organic samples smaller than 1000 mu-g C. A description of the process leading to a modified combustion method for smaller organic samples is given in detail. In addition to analyzing different background materials, the influence of different chemical reagents on the overall radiocarbon background level was investigated, such as carbon contamination arising from copper oxide of different purities and from different suppliers. Using the modified combustion method, small amounts of background materials and known-age standard IAEA-C5 were individually combusted to CO2. Below 1000 g C, organic background levels follow an inverse mass dependency when combusted with the modified method, increasing from 0.13 +/- 0.05 pMC up to 1.20 +/- 0.04 pMC for 80 mu-g C. Results for a given carbon mass were lower for combustion of etched Iceland spar calcite mineral, indicating that part of the observed background of bituminous coal was probably introduced by handling the material in atmosphere prior to combustion. Using the modified combustion method, the background-corrected activity of IAEA-C5 agreed to within 2 sigma of the consensus value of 23.05 pMC down to a sample mass of 55 mu-g C.
    • Is it Possible to Find a Good Point Estimate of a Calibrated Radiocarbon Date?

      Michczyński, Adam (Department of Geosciences, The University of Arizona, 2007-01-01)
      The result from probabilistic calibration of a radiocarbon date is given in the form of a probability density function. Consequently, reporting a 68% or 95% confidence interval has became a commonly accepted practice. However, many users of 14C dates still try to present the results of calibration as a single point. This manner of presentation is often applied during the construction of age-depth models due to its convenience and simplicity. In this paper, the author tests whether it is possible to find a good point estimate of a calibrated 14C date. The idea of the tests is to compare, using computer simulation, the true value of the calendar age with the age calculated based on the probabilistic calibration of the 14C date and the method of finding the point estimate. The test is carried out for the following point estimates: mode, median, average, the central point of the confidence intervals, and the local mode inside the confidence intervals. The results show that none of these may be considered as a good estimate.
    • Accurate Lacustrine and Wetland Sediment Accumulation Rates Determined from 14C Activity of Bulk Sediment Fractions

      Walker, W. G.; Davidson, Gregg R.; Lange, Todd; Wren, Daniel (Department of Geosciences, The University of Arizona, 2007-01-01)
      In the absence of identifiable macrofossils in lacustrine sediments, radiocarbon dating must rely on pollen or bulk sediment fractions. Bulk sediment fractions are not generally preferred because they contain an unknown mixture of organic material of variable age, they may contain dead carbon such as lignite that is difficult to eliminate, and material of aquatic origin may be subject to reservoir effects. If the various processes that contribute carbon to the system are relatively constant over time, however, changes in 14C activity with depth may be used to accurately estimate sediment accumulation rates even if the absolute ages are erroneous. In this study, fine-grained fractions (250-710 m organic material, humic acids extracted from
    • The Feasibility of Using Melanopsis Shells as Radiocarbon Chronometers, Lake Kinneret, Israel

      Lev, Lilach; Boaretto, Elisabetta; Heller, Joseph; Marco, Shmuel; Stein, Mordechai (Department of Geosciences, The University of Arizona, 2007-01-01)
      We investigated the feasibility of using Melanopsis shells as radiocarbon chronometers of paleolakes and springs in the Jordan Valley, Israel. For this purpose, we analyzed the 14C content of aragonite of living Melanopsis shells from different freshwater bodies of the northern Jordan Valley and Lake Kinneret (Sea of Galilee) and compared them to the contemporaneous water values. The Melanopsis shells are in 14C equilibrium with their habitat waters, allowing to specify a particular reservoir age for various water types. We measured ~750 yr for Lake Kinneret, ~2300 yr for northern Jordan, ~4600 yr for springs in the north Kinneret, and ~7200 yr for streams flowing directly from carbonate aquifers. These results were tested and corroborated by analyzing fossil Melanopsis shells of known age, measured on contemporaneous organic matter. We conclude that Melanopsis shells are reliable 14C chronometers and have the potential to be used as paleohydrological tracers.
    • The End of Empire: New Radiocarbon Dates from the Ayacucho Valley, Peru, and Their Implications for the Collapse of the Wari State

      Finucane, Brian Clifton; Valdez, J. Ernesto; Pérez Calderon, Ismael; Vivanco Pomacanchari, Cirilo; Valdez, Lidio M.; O'Connell, Tamsin (Department of Geosciences, The University of Arizona, 2007-01-01)
      This paper presents a suite of new accelerator mass spectrometry (AMS) radiocarbon measurements from the Ayacucho Valley of Peru and discusses their implications for the timing and nature of the collapse of the Wari Empire. Analysis of these and previously published dates from the region indicate that there is little evidence for state political authority in Ayacucho prior to the end of the 7th century. Dated human remains from the politys eponymous capital indicate that the authority of the states rulers persisted at least as late as the mid-11th century. Dates from rural sites in the Ayacucho Valley suggest continuity of occupation and folk material culture following Waris disintegration. Finally, AMS measurements of bone from 2 large extramural ossuaries represent the first absolute dates associated with Chanca ceramics and suggest that this archaeological/ethnohistoric culture appeared in the valley at about AD 1300.
    • Methods for High-Precision 14C AMS Measurement of Atmospheric CO2 at LLNL

      Graven, Heather D.; Guilderson, Thomas P.; Keeling, Ralph F. (Department of Geosciences, The University of Arizona, 2007-01-01)
      Development of radiocarbon analysis with precision better than 2 has the potential to expand the utility of 14CO2 measurements for carbon cycle investigations as atmospheric gradients currently approach the typical measurement precision of 25. The accelerator mass spectrometer at Lawrence Livermore National Laboratory (LLNL) produces high and stable beam currents that enable efficient acquisition times for large numbers of 14C counts. One million 14C atoms can be detected in approximately 25 min, suggesting that near 1 counting precision is economically feasible at LLNL. The overall uncertainty in measured values is ultimately determined by the variation between measured ratios in several sputtering periods of the same sample and by the reproducibility of replicate samples. Experiments on the collection of 1 million counts on replicate samples of CO2 extracted from a whole air cylinder show a standard deviation of 1.7 in 36 samples measured over several wheels. This precision may be limited by the reproducibility of oxalic acid I standard samples, which is considerably poorer. We outline the procedures for high-precision sample handling and analysis that have enabled reproducibility in the cylinder extraction samples at the 2 level and describe future directions to continue increasing measurement precision at LLNL.
    • Author index

      Department of Geosciences, The University of Arizona, 2007-01-01
    • The Effect of N2O, Catalyst, and Means of Water Vapor Removal on the Graphitization of Small CO2 Samples

      Smith, A. M.; Petrenko, Vasilii V.; Hua, Quan; Southon, John; Brailsford, Gordon (Department of Geosciences, The University of Arizona, 2007-01-01)
      The effect of nitrous oxide (N2O) upon the graphitization of small (~40 g of carbon) CO2 samples at the ANSTO and University of California, Irvine, radiocarbon laboratories was investigated. Both laboratories produce graphite samples by reduction of CO2 over a heated iron catalyst in the presence of an excess of H2. Although there are significant differences between the methods employed at each laboratory, it was found that N2O has no effect upon the reaction at levels of up to 9.3% by volume of CO2. Further, it was systematically determined that more effective water vapor trapping resulted in faster reaction rates. Using larger amounts of the Fe catalyst generally resulted in higher yields or reaction rates (but not both). The effects of changing the type of Fe catalyst on the final yield and reaction rate were less clear.
    • Chronological Framework of the Siberian Paleolithic: Recent Achievements and Future Directions

      Kuzmin, Yaroslav V. (Department of Geosciences, The University of Arizona, 2007-01-01)
      In Siberia, the accumulation of radiocarbon dates from archaeological sites since the 1960s makes it possible to compile a general Paleolithic 14C database, which contains about 440 entries as of late 2005. With these data, we can reveal the main chronological patterns of Paleolithic complexes, with a focus on the late Middle Paleolithic (Mousterian) and Upper Paleolithic. The 14C dates for late Middle Paleolithic industries in Siberia are quite young, up to about 30,000-28,500 BP and perhaps ~27,000 BP. The emergence of the Upper Paleolithic in Siberia took place relatively early compared with Eastern Europe. At about 43,000-35,000 BP, blade-dominated industries existed in the Altai Mountains and Lake Baikal region, and numerous adornments are known from several sites of that age. The late Upper Paleolithic complexes with microblade technology from the Altai Mountains are 14C dated to about 35,000-28,000 BP, and represent the earliest unequivocal evidence of microblade manufacture in northern Eurasia. The end of the Paleolithic in Siberia is related to the appearance of pottery, which indicates the beginning of the Neolithic period. In northern Transbaikal, the earliest pottery complexes are dated to about 12,000-11,000 BP and in the Russian Far East even to ~13,000 BP, while in most of Siberia they date to approximately 8000-6000 BP. The most important features of the Siberian Paleolithic chronology are: a) the long persistence of Middle Paleolithic complexes, until about 30,000-27,000 BP; b) very early Middle to Upper Paleolithic transition, ~43,000 BP, closely connected with the emergence of art and symbolic behavior in the earliest Upper Paleolithic at this time; c) the very early origin of microblade complexes, at least at about 35,000 BP; and d) a gradual PaleolithicNeolithic transition, beginning in the Russian Far East at ~13,000 BP and in Transbaikal about 12,000-11,000 BP, in most of Siberia at about 8000-6000 BP, and even later in some northern regions.
    • Construction of the Calendar Timescale for Lake Wigry (NE Poland) Sediments on the Basis of Radiocarbon Dating

      Piotrowska, N.; Hajdas, I.; Bonani, G. (Department of Geosciences, The University of Arizona, 2007-01-01)
      A radiocarbon chronology of lake sediments deposited in Lake Wigry during the Last Glacial and Holocene periods provided the basis for calendar age-depth modeling. Various fractions (organics and carbonates) were dated and the results were subjected to critical analysis. The dates affected by reservoir effects as well as outlying data were excluded, and the non-linear age model was developed based on 13 ages. The statistical tools used for construction of the models include the Bayesian analysis, applied for calibration of 14C dates with regard to stratigraphical position of the samples, and generalized additive models (GAM).
    • 14C Ages of 43 Consecutive Single-Year Tree Rings Between 2710 and 2655 cal BP Using Accelerator Mass Spectrometry

      Suzuki, Kayo; Sakurai, Hirohisa; Takahashi, Yui; Gunji, Shuichi; Tokanai, Fuyuki; Matsuzaki, Hiroyuki; Sunohara, Yoko (Department of Geosciences, The University of Arizona, 2007-01-01)
      We have measured the radiocarbon ages of 43 consecutive single-year tree rings using accelerator mass spectrometry (AMS) with a statistical accuracy of -2.3 AMS 14C ages of the 36 viable samples are between 2708 and 2666 cal BP, a period in which the 14C of the IntCal04 curve (Reimer et al. 2004) shows an enhancement. The 14C ages of the samples are scattered with a Gaussian distribution around the interpolated IntCal04 calibration curve. The time profile of the deviations of the 36 14C ages from the interpolated IntCal04 calibration curve indicates a linear trend and a characteristic variability rather than a random fluctuation around the curve. The trend indicates a higher gradient than that of the interpolated IntCal04 calibration curve. The profile implies a periodic variation of approximately 11 yr and an amplitude of roughly 18 14C yr.
    • Dating of the Old Bridge in Mostar, Bosnia and Herzegovina

      Obelić, Bogomil; Krajcar Bronić, Ines; Barešić, Jadranka; Peković, Zeljko; Milošević, Ante (Department of Geosciences, The University of Arizona, 2007-01-01)
      The famous single-arch stone bridge over the Neretva River in Mostar, Bosnia and Herzegovina, was built in 1557-1566 by the order of Ottoman Sultan Sleyman the Magnificent. During the reconstruction of the Old Bridge, which was destroyed during the war in 1993, remnants of 2 older wooden bridges were found at the same location. Six wood and 2 charcoal samples were dated using the radiocarbon method. Wood samples with visible tree rings were taken for dendrochronological dating. The results point to several periods of construction and repairs to the bridge and the towers at each end, spanning from the 12th to 18th century. Calibrated 14C and dendrochronological ages were in good agreement.
    • Radiocarbon Sample Preparation at the Circe AMS Laboratory in Caserta, Italy

      Passariello, Isabella; Marzaioli, Fabio; Lubritto, Carmine; Rubino, Mauro; D'Onofrio, Antonio; De Cesare, Nicola; Borriello, Gianluca; Casa, Giovanni; Palmieri, Antonio; Rogalla, Detlef; et al. (Department of Geosciences, The University of Arizona, 2007-01-01)
      A system with several lines for the preparation of graphite targets for radiocarbon analysis has been built at the new accelerator mass spectrometry (AMS facility in Caserta, Italy. Special attention has been paid in the design to the reduction of background contamination during sample preparation. Here, we describe the main characteristics of these preparation lines. Results of tests performed to measure 14C background levels and isotope fractionation in several blank samples with the Caserta AMS system are presented and discussed.
    • Do Riparian Plants Fix CO2 Lost by Evasion from Surface Waters? An Investigation Using Carbon Isotopes

      Garnett, M. H.; Billett, M. F. (Department of Geosciences, The University of Arizona, 2007-01-01)
      Rivers and streams in many parts of the world contain high concentrations of dissolved carbon dioxide, which is lost to the atmosphere by evasion (outgassing). Recent methodological advances now enable the carbon isotopic composition of this evaded CO2 to be measured directly, with early results from peatland streams showing it to be depleted in 13C relative to the atmosphere. The first direct measurements of the radiocarbon age of evaded CO2 for a stream draining a peatland site in the United Kingdom covered a large range, ranging from modern to >1400 yr BP. We investigated whether a proportion of the carbon fixed by plants growing adjacent to the stream was derived from evasion; this would have implications for the cycling of carbon in such streams, and lead to riparian plants having older, rather than contemporary, 14C ages. 13C analysis of riparian plants at the site suggested that up to 20% of the carbon they fixed was derived from evasion. Although the 14C content of the same samples suggested a similar proportion of plant carbon was derived from evaded CO2, the uncertainty in these estimates was greater. Fixation of evaded CO2 was greatest in plants growing within 1 m of the stream. Although the results for this site suggest a small amount of CO2 lost by evasion from the stream surface is incorporated in plant material, it may be a more important factor at other sites characterized by higher evasion rates, lower wind speeds, and different stream bank morphology.
    • Decadal Changes of Bomb Radiocarbon in the Subtropical South Pacific Ocean Between 1992 and 2003

      Kumamoto, Yuichiro; Murata, Akihiko; Watanabe, Shuichi; Fukasawa, Masao (Department of Geosciences, The University of Arizona, 2007-01-01)
      A basin-scale repeat hydrography of the WOCE-P06 line along approximately 32S has revealed decadal changes of bomb-produced radiocarbon in the subtropical South Pacific Ocean between 1992 and 2003. Surface ∆14C decreased by about 30. A ∆14C decrease was also found in the upper thermocline from the surface to 400 m water depth. In the lower thermocline, from 400 m to 1100 m depth, however, ∆14C increased, with a maximum increase of 25 at 700 m depth. This contrast between the upper and lower thermoclines resulted in an overall 10% increase of the specific column inventory of bomb 14C from 1992 to 2003. The global ocean inventory of bomb 14C was assessed based on the specific inventory increase in the subtropical South Pacific Ocean. The meridional distribution of bomb 14C in the early 1990s suggests that the bomb 14C increases observed along 32S in 2003 were primarily caused by mixing along isopycnals.
    • Dating the Tavan Tolgoi Site, Mongolia: Burials of the Nobility from Genghis Khans Era

      Youn, M.; Kim, J. C.; Kim, H. K.; Tumen, D.; Navaan, D.; Erdene, M. (Department of Geosciences, The University of Arizona, 2007-01-01)
      The Tavan Tolgoi (Five Holy Hills) site, located in Ongon sum, Sukhbaatar aimag, in southeastern Mongolia, consists of about 20 burials. During the preliminary 2004 excavations conducted by the Department of Anthropology and Archaeology, National University of Mongolia, 7 graves were unearthed. In grave 1 (2004), the skeleton of a woman 40 yr old, wearing golden rings with the inscription of a Siberian falcon, was found together with other ornamental artifacts. In grave 2 (2004), a man with a gold-gilded saddle and a horse were buried. Adornments strongly indicate that these burials date to the Great Mongol Empire period and may relate to the Golden Horde lineage of Genghis Khan. Initial accelerator mass spectrometry (AMS) radiocarbon dating of wood from a coffin at burial 2004-6 (Table 1) gave an age of 860 +/- 60 BP, and the age of a human bone sample from burial 2004-1 was determined as 890 +/- 40 BP. Subsequent excavations yielded 13 samples for 14C dating, and 7 of them have been dated thus far. The calibrated dates were in the range of AD 1130-1250, which is in agreement with Genghis Khans life span. Artifacts strongly suggest that these burials belong to nobility or members of the royal family. Given that such burials are hard to find, the Tavan Tolgoi site is expected to yield important archaeological and historical information. In this paper, the historical importance of the artifacts recovered is discussed in light of 14C dating and the results of additional scientific analyses.