• 14C and the Iron Age Chronology Debate: Rehov, Khirbet En-Nahas, Dan, and Megiddo

      Finkelstein, Israel; Piasetzky, Eli (Department of Geosciences, The University of Arizona, 2006-01-01)
      A recently published volume, the Bible and Radiocarbon Dating: Archaeology, Text and Science (Levy and Higham 2005), provides data related to the debate over the chronology of the Iron Age strata in the Levant (for a review, see Carmi 2006). The present article comments on several chapters in the volume. The article highlights methodological problems, such as insecure stratigraphic provenance of 14C samples, and demonstrates how unjustified selection of data can bias the result. The article offers a new interpretation to some of the results and shows that the full set of measurements from Tel Rehov supports the Low Chronology system.
    • Radiocarbon Laboratory at the National Autonomous University of Mexico: First Set of Samples and New 14C Internal Reference Material

      Beramendi-Orosco, Laura E.; Gonzalez-Hernandez, Galia; Urrutia-Fucugauchi, Jaime; Morton-Bermea, Ofelia (Department of Geosciences, The University of Arizona, 2006-01-01)
      This contribution reports the first set of samples and the creation of an internal reference material at the recently opened Radiocarbon Laboratory at the National Autonomous University of Mexico (UNAM). Samples for the initial measurements were selected from archaeological and dating projects on Teotihuacán, one of the largest and best-studied Mesoamerican urban and ceremonial centers. The 14C dates were compared to results obtained by 2 other laboratories in order to assess the results obtained at UNAM and validate the adopted methodology. As part of the quality assurance protocol, an internal reference material was created that consists of charred wood from the Teotihuacán site with a 14C activity in the value range expected for samples from Mesoamerican archaeological sites. Results from 7 analyses have a mean of 1750 +/16 BP (80.43 +/0.16 pMC).
    • Radiocarbon Dating of Soil Organic Matter Fractions in Andosols in Northern Ecuador

      Tonneijck, Femke H.; van der Plicht, Johannes; Jansen, Boris; Verstraten, Jacobus M.; Hooghiemstra, Henry (Department of Geosciences, The University of Arizona, 2006-01-01)
      Volcanic ash soils (Andosols) may offer great opportunities for paleoecological studies, as suggested by their characteristic accumulation of organic matter (OM). However, understanding of the chronostratigraphy of soil organic matter (SOM) is required. Therefore, radiocarbon dating of SOM is necessary, but unfortunately not straightforward. Dating of fractions of SOM obtained by alkali-acid extraction is promising, but which fraction (humic acid or humin) renders the most accurate 14C dates is still subject to debate. To determine which fraction should be used for 14C dating of Andosols and to evaluate if the chronostratigraphy of SOM is suitable for paleoecological research, we measured 14C ages of both fractions and related calibrated ages to soil depth for Andosols in northern Ecuador. We compared the time frames covered by the Andosols with those of peat sequences nearby to provide independent evidence. Humic acid (HA) was significantly older than humin, except for the mineral soil samples just beneath a forest floor (organic horizons), where the opposite was true. In peat sections, 14C ages of HA and humin were equally accurate. In the soils, calibrated ages increased significantly with increasing depth. Age inversions and homogenization were not observed at the applied sampling distances. We conclude that in Andosols lacking a thick organic horizon, dating of HA renders the most accurate results, since humin was contaminated by roots. On the other hand, in mineral soil samples just beneath a forest floor, humin ages were more accurate because HA was then contaminated by younger HA illuviated from the organic horizons. Overall, the chronostratigraphy of SOM in the studied Andosols appears to be suitable for paleoecological research.
    • Radiocarbon Dating and Balearic Prehistory: Reviewing the Periodization of the Prehistoric Sequence

      Mic, Rafael (Department of Geosciences, The University of Arizona, 2006-01-01)
      The Balearic Islands are one of the most widely dated regions in Europe, totaling about 800 dates. The aim of this paper is to propose an updated periodization for the prehistory of Majorca and Minorca based on the analysis of a series of absolute dates for over 100 archaeological sites and in combination with a critical assessment of the associated contextual information. Only by means of a solid chronological scheme will we then be able to approach research into the social significance of the vast archaeological record that the islands has to offer and also make reliable comparisons with developments in surrounding regions.
    • Radiocarbon Laboratories

      Department of Geosciences, The University of Arizona, 2006-01-01
      This is Radiocarbon's annual list of active radiocarbon laboratories and personnel known to us. Conventional beta-counting facilities are listed in Part I, and accelerator mass spectrometry (AMS) facilities are listed in Part II. Laboratory code designations, used to identify published dates, are given to the left of the listing. (See p 515 for a complete list of past and present lab codes.)
    • Over 16,000 Years of Fire Frequency Determined from AMS Radiocarbon Dating of Soil Charcoal in an Alluvial Fan at Bear Flat, Northeastern British Columbia

      Jull, A. J. Timothy; Geertsema, Marten (Department of Geosciences, The University of Arizona, 2006-01-01)
      We present results of radiocarbon dating of charcoal from paleosols and buried charcoal horizons in a unique sequence, which potentially records the last 36,000 yr, from a fan at Bear Flat, British Columbia (BC) (56 degrees 16'51"N, 121 degrees 13'39"W). Evidence for forest-fire charcoal is found over the last 13,500 +/110 14C yr before present (BP) or 16,250 +/700 cal BP. The study area is located east of the Rocky Mountains in an area that was ice-free at least 13,970 +/170 14C yr BP (17,450-16,150 cal BP) ago. The latest evidence of fire is during the Medieval Warm Period (MWP). The charcoal ages show a periodicity in large fires on a millennial scale through the Holocene—an average of 4 fires per thousand years. Higher fire frequencies are observed between 2200 to 2800 cal BP, ~5500 and ~6000 cal BP, ~7500 to 8200 cal BP, and 9000 to 10,000 cal BP. These intervals also appear to be times of above-average aggradation of the fan. We conclude that fire frequency is related to large-scale climatic events on a millennial time scale.
    • Quantitative Determination by 14C Analysis of the Biological Component in Fuels

      Dijs, Ivo J.; van der Windt, Eric; Kaihola, Lauri; van der Borg, Klaas (Department of Geosciences, The University of Arizona, 2006-01-01)
      Radiocarbon analysis was performed by liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) to assess whether the content of biological components in hydrocarbon fuels could be derived. Different fuel mixtures were prepared containing bioethanol, fossil ethanol, and fossil gasoline. The specific 14C activity of these mixtures was obtained from LSC measurements and directly related to the concentration of carbon originating from the bioethanol (biocarbon). The results were checked via standardized carbon dating procedures and AMS. A good linear correlation exists between the fuel mixtures specific 14C activity and the concentration of biocarbon. Also, the biocarbon fraction of the fuel mixture (the ratio biocarbon : total carbon) and the normalized fraction of biocarbon (%M) showed good linear correlation. Therefore, both relations provide a possibility to quantitatively determine a fuels biocarbon content by 14C analysis. When the sample composition is known (e.g. Resolved by gas chromatography-mass spectroscopy [GC-MS] and nuclear magnetic resonance [NMR]), the amount of particular biological components in a fuel sample can be derived subsequently. For mixtures of bioethanol, fossil ethanol, and gasoline with bioethanol contents in the range of 0.52% m/m, it was found that errors in the normalized fraction of biocarbon (%M) were in the range of 2510%, respectively. For samples with a higher bioethanol content (up to pure bioethanol), the errors in %M were 10%. Errors might be larger if substantial changes in the concentration of atmospheric 14C took place during the growth period of the biofuel feedstock. By taking into account the variation in specific 14C activity of carbon over the last decades, and by modeling simple tree-growth, it could be illustrated that this effect becomes significant only if the biofuel feedstock stopped growing more than 1 decade ago, e.g. With wood from constructions.
    • Radiocarbon Dating Sites of Itaparica Dam, São Francisco River Valley, Brazil

      de Andrade Lima, L. R. P. (Department of Geosciences, The University of Arizona, 2006-01-01)
      This paper reports radiocarbon dates of samples from archaeological sites in the Itaparica Dam region of the So Francisco River (Brazil). This region is important due to the evidence of its use by several prehistoric groups of huntergatherers. In the 1980s, a Brazilian state hydroelectric company (CHESF) engaged the federal universities of Bahia and Pernambuco to perform an archaeological rescue excavation at the Itaparica Dam reservoir area. This excavation allowed the collection of a large number of ceramics and lithic artifacts as well as fireplace charcoal. In this study, fireplace charcoal samples from the Bahia State riverside of the Itaparica Dam were selected and used for dating purposes. The 14C ages were between 3840 and 210 BP, and the values of d13C range from -22.93 to -24.81ppm. The 14C dates, in addition to the archaeological findings, indicate that the presence of humans in the region was contemporary with the intermediate levels of older sites found in the adjacent area, and also indicate different settlement periods.
    • Response to Moss et al. “An Early Holocene/Late Pleistocene Archaeological Site on the Oregon Coast? Comments on Hall et al. (2005)”

      Davis, Loren G.; Hall, Roberta A.; Willis, Samuel C. (Department of Geosciences, The University of Arizona, 2006-01-01)
      Moss et al. (2006) provided comments and criticisms of our recent paper in this journal (Hall et al. 2005). We can appreciate the need for promoting vigorous dialogue among those interested in the research of early sites along the New World Pacific Margin and thus welcome their intervention; however, we are compelled to respond because they raise several points that require clarification and introduce a critical error that must be corrected.
    • A Preliminary Assessment of Age at Death Determination Using the Nuclear Weapons Testing 14C Activity of Dentine and Enamel

      Cook, Gordon T.; Dunbar, Elaine; Black, Sue M.; Xu, Sheng (Department of Geosciences, The University of Arizona, 2006-01-01)
      Calibration (using CALIBomb) of radiocarbon measurements made on the enamel of human teeth from people born during the nuclear era typically produce 2 possible age ranges that potentially reflect the period of tooth formation. These ranges correspond to periods before and after the 1963 atmospheric 14C maximum. Further measurements made on the collagen component of the combined dentine and cementum from the roots of the same teeth enable the appropriate age range to be selected. Using this range and the formation times for individual teeth, we estimated the year of birth of the individuals and compared these to the known dates of birth. The results were relatively accurate and confirmed those of a previous study by another research group. The present study demonstrates that it is possible to produce a good estimate of the year of birth from a single tooth.
    • Radioactive Graphite Dispersion in the Environment in the Vicinity of the Chernobyl Nuclear Power Plant

      Buzinny, Michael (Department of Geosciences, The University of Arizona, 2006-01-01)
      This paper estimates the radioactive graphite dispersion on the land surface (forest litter and soil) as a result of the Chernobyl Nuclear Power Plant (NPP) release. Graphite mass was calculated using an estimated average concentration of 2.5 x 10^7 Bq/kg C (carbon). The sample collection method, sample origin and its mass, and sample preparation procedure used for preparation of benzene were taken into account to obtain the optimum sensitivity of the method. Thus, the sensitivity of the corresponding method for graphite detection in forest litter was estimated to be 0.2 mg/m2. All analyses gave a range of deposited graphite from 0.12 to 52.6 mg/m2. The maximum value was observed at a site located 9 km west of the Chernobyl NPP. The results of the study indicate the importance of studying the upper layer of soil (05 cm) in addition to the lower layer of forest litter.
    • Society Islands (Central Eastern Polynesia) Chronology: 11 Radiocarbon Dates for the Late Prehistoric Expansion and Proto-Historic Periods in the Opunohu Valley, Moorea

      Kahn, Jennifer G. (Department of Geosciences, The University of Arizona, 2006-01-01)
      The chronology of residential site construction and occupation in the upper reaches of the Opunohu Valley, Moorea, Central Eastern Polynesia, has been debated over the last 15 yr. This paper reports a suite of 11 radiocarbon age determinations from excavations at 5 house sites and a simple temple structure (marae). Direct accelerator mass spectrometry (AMS) dating of wood charcoal identified to short-lived taxa confirms site construction and occupation during the mid-15th to 17th centuries, supporting that maximal population density was in the centuries immediately prior to European contact. The study demonstrates that targeted dating of multiple structures within residential complexes allows for multiple phases of site construction and use to be discriminated. These data are critical for adequately assessing site contemporaneity and the development, maintenance, and expansion of residential groups and their house clusters through time.
    • 14C Dating of ~2500-Yr-Old Choukai Jindai Cedar Tree Rings from Japan Using Highly Accurate LSC Measurement

      Sakurai, Hirohisa; Kato, Wataru; Takahashi, Yosuke; Suzuki, Kayo; Takahashi, Yui; Gunji, Shuichi; Tokanai, Fuyuki (Department of Geosciences, The University of Arizona, 2006-01-01)
      Radiocarbon ages of 8 decadal tree rings and 66 single-yr tree rings have been measured with a highly accurate liquid scintillation counting (LSC) system (0.2% error) after synthesizing 10.5 g of benzene for each a-cellulose sample produced from tree rings of Choukai Jindai cedar in Japan (39 degrees N). The 14C ages were between 2449 and 2539 14C yr BP for the 21 samples. From the wiggle-matching of the data set using the IntCal04 (Reimer et al. 2004) calibration data in OxCal v 3.10 (Bronk Ramsey 2005), the estimated age of the outer edge of the Choukai tree rings was 477.5 BC (+/12.5 yr) with a confidence level of 95.5%; hence, the Choukai tree rings range from 2757 to 2437 cal BP. The age indicates an improved eruption date of the Choukai Volcano. The statistical errors at 1 sigma are approximately +/10 and +/7 14C yr for the 5-yr data and the decadal data from the single-yr measurements, respectively. For the interval between 2580 and 2520 cal BP, it is statistically significant that the Choukai 14C ages are ~16 14C yr older on average than both the IntCal04 and QL German oak (~50 degrees N) data sets. The ~2.0 offset is informative for the study of regional offset in the Far East.
    • ENEA Radiocarbon Measurements II

      Magnani, Giuseppe; Bartolomei, Paolo; La Torretta, Teresa; Marino, Ernesto Claudio (Department of Geosciences, The University of Arizona, 2006-01-01)
      This paper includes determinations of geological samples coming from the Emilia Romagna region (northern Italy) performed at the ENEA Radiocarbon Laboratory. These analyses were executed as part of the Geological Cartography (CARG) project aimed to realize a new Italian Geological Map.
    • How to Convert Biological Carbon Into Graphite for AMS

      Getachew, Girma; Kim, Seung-Hyun; Burri, Betty J.; Kelly, Peter B.; Haack, Kurt W.; Ognibene, Ted J.; Buchholz, Bruce A.; Vogel, John S.; Modrow, Jonathan; Clifford, Andrew J. (Department of Geosciences, The University of Arizona, 2006-01-01)
      Isotope tracer studies, particularly radiocarbon measurements, play a key role in biological, nutritional, and environmental research. Accelerator mass spectrometry (AMS) is now the most sensitive detection method for 14C, but AMS is not widely used in kinetic studies of humans. Part of the reason is the expense, but costs would decrease if AMS were used more widely. One component in the cost is sample preparation for AMS. Biological and environmental samples are commonly reduced to graphite before they are analyzed by AMS. Improvements and mechanization of this multistep procedure is slowed by a lack of organized educational materials for AMS sample preparation that would allow new investigators to work with the technique without a substantial outlay of time and effort. We present a detailed sample preparation protocol for graphitizing biological samples for AMS and include examples of nutrition studies that have used this procedure.
    • High-Accuracy 14C Measurements for Atmospheric CO2 Samples by AMS

      Meijer, H. J.; Pertuisot, M. H.; van der Plicht, J. (Department of Geosciences, The University of Arizona, 2006-01-01)
      In this paper, we investigate how to achieve high-accuracy radiocarbon measurements by accelerator mass spectrometry (AMS) and present measurement series (performed on archived CO2) of 14CO2 between 1985 and 1991 for Point Barrow (Alaska) and the South Pole. We report in detail the measurement plan, the error sources, and the calibration scheme that enabled us to reach a combined uncertainty of better than 3. The d13C correction and a suggestion for a span (or 2point) calibration for the 14C scale are discussed in detail. In addition, we report new, accurate values for the calibration and reference materials Ox2 and IAEA-C6 with respect to Ox1. The atmospheric 14CO2 records (1985-1991) are presented as well and are compared with other existing records for that period. The Point Barrow record agrees very well with the existing Fruholmen (northern Norway) record from the same latitude. The South Pole record shows a small seasonal cycle but with an extreme phase with a maximum on January 1st (+/13 days). Together with its generally elevated 14C level compared to the Neumayer record (coastal Antarctica), this makes our South Pole data set a valuable additional source of information for global carbon cycle modeling using 14CO2 as a constraint.
    • Intrashell Radiocarbon Variability in Marine Mollusks

      Culleton, Brendan J.; Kennett, Douglas J.; Ingram, B. Lynn; Erlandson, Jon M.; Southon, John R. (Department of Geosciences, The University of Arizona, 2006-01-01)
      We demonstrate variable radiocarbon content within 2 historic (AD 1936) and 2 prehistoric (about 8200 BP and 3500 BP) Mytilus californianus shells from the Santa Barbara Channel region, California, USA. Historic specimens from the mainland coast exhibit a greater range of intrashell variability (i.e. 180-240 14C yr) than archaeological specimens from Daisy Cave on San Miguel Island (i.e. 120 14C yr in both shells). d13C and d18O profiles are in general agreement with the upwelling of deep ocean water depleted in 14C as a determinant of local marine reservoir correction (Delta-R) in the San Miguel Island samples. Upwelling cycles are difficult to identify in the mainland specimens, where intrashell variations in 14C content may be a complex product of oceanic mixing and periodic seasonal inputs of 14C-depeleted terrestrial runoff. Though the mechanisms controlling Delta-R at subannual to annual scales are not entirely clear, the fluctuations represent significant sources of random dating error in marine environments, particularly if a small section of shell is selected for accelerator mass spectrometry (AMS) dating. For maximum precision and accuracy in AMS dating of marine shells, we recommend that archaeologists, paleontologists, and 14C lab personnel average out these variations by sampling across multiple increments of growth.