• A Radiocarbon Chronology of Hunter-Gatherer Occupation from Bodega Bay, California, USA

      Kennedy, Michael A.; Russell, Ann D.; Guilderson, Tom P. (Department of Geosciences, The University of Arizona, 2005-01-01)
      We present a Holocene radiocarbon chronology of hunter-gatherer occupation based on contemporaneous samples of charcoal and Mytilus californianus shell recovered from 7 archaeological sites near Bodega Bay, California, USA. A series of 127 14C ages reveals a chronological sequence that spans from 8940-110 cal BP (1 sigma). This sequence serves as a foundation for the interpretation of behavioral change along the northern California coast over the last 9000 yr, including the adaptive strategies used by human foragers to colonize and inhabit coastal areas of this region. These 14C ages will also permit us to explore major dimensions of temporal change in Holocene ocean conditions (via marine reservoir corrections) and their potential effect on the resources available to ancient hunter-gatherers.
    • A Simple, Extremely Stable Single-Tube Liquid Scintillation System for Radiocarbon Dating

      Theodórsson, Páll (Department of Geosciences, The University of Arizona, 2005-01-01)
      This paper describes a simple and compact liquid scintillation radiocarbon dating system, ICELS, and demonstrates its long-term stability and reproducibility to a precision level rarely presented before, better than 0.04% (3 14C yr). Inexpensive systems of this kind may, in the future, help to meet increasing demand for high precision (+/16 to +/20 14C yr) and strict quality control. ICELS comprises a compact detector unit, where a 3-mL dome-shaped vial, with an optimal light reflector, sits on the top of a vertical 30-mm photomultiplier tube. Sample changing is manual. The high voltage is set at the balance point for each sample, securing maximal counting stability. The quench correction method used (spectrum restoration) corrects with 0.04% precision for all parameters that can normally shift the 14C spectrum. For 3 mL of benzene at 71% 14C counting efficiency (recent carbon 23 cpm), the background is 1.72 cpm behind a 5-cm-thick shield of lead (27 kg) and 1.53 cpm behind 10 cm of lead. The background count rate corrected for atmospheric pressure variations was completely stable over 47and 57-d testing periods for the 2 systems.
    • AMS 14C Dating of Pollen Concentrate from Late Pleistocene ICE Wedges from the Bison and Seyaha Sites in Siberia

      Vasil'chuk, Alla; Kim, Jong-Chan; Vasil'chuk, Yurij (Department of Geosciences, The University of Arizona, 2005-01-01)
      Accelerator mass spectrometry (AMS) radiocarbon dates of pollen concentrate were obtained from multistage syngenetic ice wedges of cross-sections from the Late Pleistocene Bison site, located along the Lower Kolyma River (68 degrees 34'N, 158 degrees 34'E), from ~43,600 to ~26,200 BP, and 3 AMS 14C dates of pollen concentrate in ice wedges from the Seyaha site cross-section, located on the east coast of the Yamal Peninsula (70 degrees 10'N, 72 degrees 34'E), from ~22,400 to ~25,200 BP. Pollen concentrate samples were prepared using a special pretreatment procedure. Pollen and spores from ice-wedge ice signalize a regional pollen rain. Therefore, 14C-dated extracts of pollen and spores from ice-wedge ice enable an adequate reconstruction and chronology of landscape dynamics on a regional scale. The pollen and spores were well preserved despite numerous redepositions in the penecontemporaneous structure in which they were found. Thus, a comparison with dates on other fractions from the same sample is necessary. The youngest date is the most reliable among the intersample AMS 14C dates from the ice and permafrost sediments.
    • AMS Radiocarbon Dates of Kurgans Located On the Ust'-Yurt Plateau, Uzbekistan

      Blau, Soren; Yagodin, Vadim (Department of Geosciences, The University of Arizona, 2005-01-01)
      Recent osteological analyses of archaeological human skeletal remains from the Ust-Yurt Plateau, Uzbekistan, provided the opportunity to obtain samples for radiocarbon dating. The results of 18 accelerator mass spectrometry (AMS) dates are presented in this paper and provide the first absolute dates for late prehistoric and early historic archaeological sites in Uzbekistan. The AMS dates suggest that most sites are earlier than have been traditionally thought based on relative dating using artifact typologies.
    • AMS Radiocarbon Dating of Bone Samples from the Xinzhai Site in China

      Liu, Kexin; Han, Baoxi; Guo, Zhiyu; Wu, Xiaohong; Yuan, Sixun; Kutschera, Walter; Ma, Hongji; Priller, Alfred; Steier, Peter; Wild, Eva Maria; et al. (Department of Geosciences, The University of Arizona, 2005-01-01)
      Xinzhai is an important archaeological site discovered 40 yr ago and recently re-excavated in the Henan Province, dynasty of China. Radiocarbon measurements on bone samples from this site were performed at the Peking University AMS facility (PKU-AMS) and the Vienna University AMS facility (VERA). Calibrated ages were obtained with the computer program OxCal. The results of these measurements are presented and the related chronology is discussed.
    • AMS Radiocarbon Dating of the Fengxi Site in Shaanxi, China

      Guo, Zhiyu; Liu, Kexin; Yuan, Sixun; Wu, Xiaohong; Li, Kun; Lu, Xiangyang; Wang, Jinxia; Ma, Hongji; Gao, Shijun; Xu, Lianggao (Department of Geosciences, The University of Arizona, 2005-01-01)
      The Fengxi site is near the Feng River in Shaanxi Province, China. Feng City was the capital of the vassal state of Zhou, and the Zhou people lived in this area until the end of the Western Zhou. Serial samples of charcoal, bone, and charred millet were collected from the site and dated by accelerator mass spectrometry (AMS). A sequence model with 6 phases of the Western Zhou dynasty was constructed and the 14C ages were calibrated with OxCal v 3.9. The results showed that the site was used from 1170-1070 BC until 825-755 BC, and the Conquest of Shang by King Wu most probably occurred during 1060-1000 BC.
    • An Assessment of Radiocarbon Dates from Palau, Western Micronesia

      Liston, Jolie (Department of Geosciences, The University of Arizona, 2005-01-01)
      Archaeological investigations in the Republic of Palau, Micronesia, have produced 409 radiocarbon age determinations from cultural contexts, indicating a range of Palauan occupation from about 3000 yr ago into the modern era. However, these dates are scattered among numerous sources (many difficult to obtain) and are presented in a number of different formats and calibrations. The goal of this paper is to compile a usable, systematic database of all of these Palauan cultural 14C assays. This database will be suitable for developing and evaluating chronological models, an effort being undertaken as a separate paper. Prior to constructing prehistoric colonization and cultural chronologies for Palau, the validity of each assay and the relative adequacy in sample size per cultural and environmental zones must be examined. After systematic recalibration, the reliability of the dates is evaluated in light of sample material, cultural context, and site formation processes. A method for dating monumental earthwork complexes through site formation analysis is presented. Sets of 237 valid and 58 potentially valid 14C dates remain to develop chronological models. The representation of Palaus environmental zones, site types, and regions within the dating pool is examined and compared to ensure meaningfulness in these chronological models. Newly obtained 14C age determinations are also provided.
    • Blank Correction for Δ14C Measurements in Organic Compound Classes of Oceanic Particulate Matter

      Hwang, Jeomshik; Druffel, Ellen R. M. (Department of Geosciences, The University of Arizona, 2005-01-01)
      Contaminant carbon (blank carbon) was studied for its impact on the carbon isotope measurements (Delta-14C and delta-13C) of 3 organic compound classes of oceanic particulate organic matter. Two methods of blank correction and associated uncertainties were studied. First, the carbon blanks were quantified manometrically and the isotope ratios of the blank carbon were measured directly. Second, the isotope ratios of the blank carbon were estimated using the standard dilution method from the difference in Delta-14C values between unprocessed and processed standards. The 2 methods agreed within the uncertainties. The standard deviations of numerous Delta-14C measurements made on processed standard compounds were comparable to those of real samples. Blank correction using the standard dilution method is much less sensitive to the error in determination of blank carbon mass than is correction using the directly measured mass and Delta-14C values of the blank carbon. The standard dilution method is recommended for correcting Delta-14C analyses of small samples that involve incorporation of a significant amount of blank carbon.
    • Book Review: Late Quaternary Environmental Change: Physical and Human Perspectives, Martin Bell, Michael J. C. Walker

      Martin, Paul S. (Department of Geosciences, The University of Arizona, 2005-01-01)
    • Carbon Dioxide Capture Using a Zeolite Molecular Sieve Sampling System for Isotopic Studies (13C and 14C) of Respiration

      Hardie, S. L.; Garnett, M. H.; Fallick, A. E.; Rowland, A. P.; Ostle, N. J. (Department of Geosciences, The University of Arizona, 2005-01-01)
      A method for collecting an isotopically representative sample of CO2 from an air stream using a zeolite molecular sieve is described. A robust sampling system was designed and developed for use in the field that includes reusable molecular sieve cartridges, a lightweight pump, and a portable infrared gas analyzer (IRGA). The system was tested using international isotopic standards (13C and 14C). Results showed that CO2 could be trapped and recovered for both d13C and 14C analysis by isotope ratio mass spectrometry (IRMS) and accelerator mass spectrometry (AMS), respectively, without any contamination, fractionation, or memory effect. The system was primarily designed for use in carbon isotope studies of ecosystem respiration, with potential for use in other applications that require CO2 collection from air.
    • Chronologies for Recent Peat Deposits Using Wiggle-Matched Radiocarbon Ages: Problems with Old Carbon Contamination

      Charman, Dan J.; Garnett, Mark H. (Department of Geosciences, The University of Arizona, 2005-01-01)
      Dating sediments which have accumulated over the last few hundred years is critical to the calibration of longer-term paleoclimate records with instrumental climate data. We attempted to use wiggle-matched radiocarbon ages to date 2 peat profiles from northern England which have high-resolution records of paleomoisture variability over the last ~300 yr. A total of 65 14C accelerator mass spectrometry (AMS) measurements were made on 33 macrofossil samples. A number of the age estimates were older than expected and some of the oldest ages occurred in the upper parts of the sequence, which had been dated to the late 19th and early 20th century using other techniques. We suggest that the older 14C ages are the result of contamination by industrial pollution. Based on counts of spheroidal carbonaceous particles (SCPs), the potential aging effect for SCP carbon was calculated and shown to be appreciable for samples from the early 20th century. Ages corrected for this effect were still too old in some cases, which could be a result of fossil CO2 fixation, non-SCP particulate carbon, contamination due to imperfect cleaning of samples, or the reservoir effect from fixation of fossil carbon emanating from deeper peat layers. Wiggle matches based on the overall shape of the depth-14C relationship and the 14C minima in the calibration curve could still be identified. These were tested against other age estimates (210Pb, pollen, and SCPs) to provide new age-depth models for the profiles. New approaches are needed to measure the impact of industrially derived carbon on recent sediment ages to provide more secure chronologies over the last few hundred years.
    • Comparative Radiocarbon Dating of Lignite, Pottery, and Charcoal Samples from Babeldaob Island, Republic of Palau

      Anderson, Atholl; Chappell, John; Clark, Geoffrey; Phear, Sarah (Department of Geosciences, The University of Arizona, 2005-01-01)
      It is difficult to construct archaeological chronologies for Babeldaob, the main island of Palau (western Micronesia), because the saprolitic clays of the dominant terraced-hill sites and associated ceramic sherds often contain old carbon that originated in lignites. This has implications, as well, for chronologies of sedimentary sequences. Comparative analysis of the dating problem using lignite, pottery, and charcoal samples indicates that, in fact, there are both old and young sources of potential contamination. It is concluded that radiocarbon samples from Babeldaob need to be tested for appropriate carbon content rather than relying solely upon material identification.
    • Dating the Iron Age I/II Transition in Israel: First Intercomparison Results

      Boaretto, Elisabetta; Jull, A. J. Timothy; Gilboa, Ayelet; Sharon, Ilan (Department of Geosciences, The University of Arizona, 2005-01-01)
      Nearly a decade ago, a different chronology than the conventional absolute chronology for the early Iron Age in Israel was suggested. The new, lower chronology transfers Iron Age I and Iron Age IIA contexts in Israel, traditionally dated to the 11th and 10th centuries BCE, to the 10th and 9th centuries, respectively. Thus, it places the Iron I/IIA transition at about 920-900 BCE. This alternative chronology carries important implications for Israelite history, historiography, and Bible research, as well as for the chronologies of other regions around the Mediterranean. Relevant radiocarbon data sets published to date, which were measured at different sites by different laboratories, were claimed to be incompatible. Therefore, the question of agreement between laboratories and dating methods needs to be addressed at the outset of any study attempting to resolve such a tight chronological dilemma. This paper addresses results pertaining to this issue as part of a comprehensive attempt to date the early Iron Age in Israel based on many sites, employing different measuring techniques in 2 laboratories. The intercomparison results demonstrate that: a) the agreement between the 2 laboratories is well within the standard in the 14C community and that no bias can be detected in either laboratory; and b) calculating the Iron I|IIa transition in 3 different ways (twice independently by the measurements obtained at the 2 labs and then by combining the dates of both) indicates that the lower chronology is the preferable one.
    • Determination of 14C in Volcanic Gas By Accelerator Mass Spectrometry

      Yoshikawa, Hideki; Nakahara, Hiromichi; Imamura, Mineo; Kobayashi, Kouichi; Nakanishi, Takashi (Department of Geosciences, The University of Arizona, 2005-01-01)
      Radioactive nuclides such as radiocarbon can be good tracers for investigating the circulation of underground carbon and water. Volcanic gas can be sampled reliably for 14C analysis and prepared for analysis by accelerator mass spectrometry (AMS). In this paper, we establish a method for the measurement of 14C in volcanic gas, and measure the amounts of 14C in various volcanic gases. Samples of fumarolic gas from some Japanese volcanoes were found to contain 0.5 to 4.2 pMC, while those from White Island in New Zealand contained 2.6 pMC. Dissolved gas from Lake Nyos, Cameroon, contained 0.4 to 4.8 pMC. The data indicate a mixing process between surface carbon and deep carbon.
    • Diet-Derived Variations in Radiocarbon and Stable Isotopes: A Case Study from Shag River Mouth, New Zealand

      Higham, Thomas; Anderson, Atholl; Bronk Ramsey, Christopher; Tompkins, Christine (Department of Geosciences, The University of Arizona, 2005-01-01)
      Accelerator mass spectrometry (AMS) determinations of rat bones from natural and cultural sites in New Zealand have produced ages at odds with the accepted date for early human settlement by over 1000 yr. Since rats are a human commensal, this implies either an earlier visitation by people or problems with the reliability of the AMS determinations. One explanation for the extreme ages is dietary variation involving movement of depleted radiocarbon through dietary food chains to rats. To investigate this, we 14C dated fauna from the previously well-dated site of Shag River Mouth. The faunal remains were of species that consumed carbon derived from a variety of environments within the orbit of the site, including the estuary, river, land, and sea. The 14C results showed a wide range in age among estuarine and freshwater species. Terrestrial and marine organisms produced ages within expectations. We also found differences between bone dated using the Oxford ultrafiltration method and those treated using the filtered gelatin method. This implies that contamination could also be of greater importance than previously thought.
    • Estimating Turnover of Soil Organic Carbon Fractions Based on Radiocarbon Measurements

      Bruun, Sander; Six, Johan; Jensen, Lars S.; Paustian, Keith (Department of Geosciences, The University of Arizona, 2005-01-01)
      In this paper, we examine 3 different models used to estimate turnover of soil organic carbon (SOC) fractions using radiocarbon measurements: one conventional carbon dating model and two bomb 14C models. One of the bomb 14C models uses an atmospheric 14C record for the period 22,050 BC to AD 2003 and is solved by numerical methods, while the other assumes a constant 14C content of the atmosphere and is solved analytically. The estimates of SOC turnover obtained by the conventional 14C dating model differed substantially from those obtained by the bomb 14C models, which we attribute to the simplifying assumption of the conventional 14C model that the whole SOC fraction is of the same age. The assumptions underlying the bomb 14C models are more applicable to SOC fractions; therefore, the calculated turnover times are considered to be more reliable. We used Monte Carlo simulations to estimate the uncertainties of the turnover times calculated with the numerically solved 14C model, accounting not only for measurement errors but also for uncertainties introduced from assumptions of constant input and uncertainties in the 14C content of the CO2 assimilated by plants. The resulting uncertainties depend on systematic deviations in the atmospheric 14C record for SOC fractions with a fast turnover. Therefore, the use of the bomb 14C models can be problematic when SOC fractions with a fast turnover are analyzed, whereas the relative uncertainty of the turnover estimates turned out to be smaller than 30% when the turnover time of the SOC fractions analyzed was longer than 30 yr, and smaller than 15% when the turnover time was longer than 100 yr.
    • Improved Tube Cracker for Opening Vacuum-Sealed Glass Tubes

      Norton, Glenn A. (Department of Geosciences, The University of Arizona, 2005-01-01)
      A variety of analytical procedures involve breaking open a glass or quartz vessel containing a gaseous sample, and then quantitatively collecting the sample gases for analysis. In order to do this, a variety of "tube crackers" have been used. This paper discusses an alternate tube cracker that offers numerous advantages over those that have been discussed previously in the literature.
    • Influence of Mollusk Species on Marine ΔR Determinations

      Ascough, Philippa L.; Cook, Gordon T.; Dugmore, Andrew J.; Scott, E. Marian; Freeman, Stewart T. (Department of Geosciences, The University of Arizona, 2005-01-01)
      Radiocarbon ages were measured on replicate samples of burnt grain and 5 mollusk species collected from a single sealed layer at an archaeological site (Hornish Point) on the west coast of South Uist, Scotland. The aim was to examine the impact of using different mollusk species on Delta-R determinations that are calculated using the paired terrestrial/marine sample approach. The mollusk species examined inhabit a range of environments and utilize a variety of food sources within the intertidal zone. Several authors have suggested that these factors may be responsible for observed variations in the 14C activity of mollusk shells that were contemporaneous in a single location. This study found no significant variation in the 14C ages of the mollusk species, and consequently, no significant variation in calculated values of Delta-R. The implication is that in an area where there are no carboniferous rocks or significant local inputs of freshwater to the surface ocean, any of a range of marine mollusk species can be used in combination with short-lived terrestrial material from the same secure archaeological context to accurately determine a R value for a particular geographic location and period in time.
    • New Bomb Pulse Radiocarbon Records from Annual Tree Rings in the Northern Hemisphere Temperate Region

      Quarta, G.; D'Elia, M.; Valzano, D.; Calcagnile, L. (Department of Geosciences, The University of Arizona, 2005-01-01)
      The bomb radiocarbon spike induced by atmospheric nuclear detonations has been reconstructed at a latitude of 40 degrees N by measuring the 14C content in annual rings of a living pine (Pinus pinea) at the Accelerator Mass Spectrometry facility of the University of Lecce. We report how the samples were taken, selected, prepared for analysis, and measured. The results are in good agreement with other data sets available for the Northern Hemisphere temperate regions, showing that a curve for the calibration of 14C dates, valid for the whole Northern Hemisphere, can be established for the second half of the 20th century.
    • Obituary (Paul Damon, 1921-2005)

      Jull, A. J. Timothy; Barbetti, Mike; Haynes, Vance (Department of Geosciences, The University of Arizona, 2005-01-01)