• Radiocarbon, Volume 45, Number 1 (2003)

      Department of Geosciences, The University of Arizona, 2003-01-01
    • From the Former Managing Editor

      Elliott, Kim (Department of Geosciences, The University of Arizona, 2003-01-01)
    • From the Editor

      Jull, A. J. Timothy (Department of Geosciences, The University of Arizona, 2003-01-01)
    • Radiocarbon Dating of Individual Fatty Acids as a Tool for Refining Antarctic Margin Sediment Chronologies

      Ohkouchi, Naohiko; Eglinton, Timothy I.; Hayes, John M. (Department of Geosciences, The University of Arizona, 2003-01-01)
      We have measured the radiocarbon contents of individual, solvent-extractable, short-chain (C14, C16, and C18) fatty acids isolated from Ross Sea surface sediments. The corresponding 14C ages are equivalent to that of the post-bomb dissolved inorganic carbon (DIC) reservoir. Moreover, molecular 14C variations in surficial (upper 15 cm) sediments indicate that these compounds may prove useful for reconstructing chronologies of Antarctic margin sediments containing uncertain (and potentially variable) quantities of relict organic carbon. A preliminary molecular 14C chronology suggests that the accumulation rate of relict organic matter has not changed during the last 500 14C yr. The focus of this study is to determine the validity of compound-specific 14C analysis as a technique for reconstructing chronologies of Antarctic margin sediments.
    • Radiocarbon Dates from Halfiah Gibli (Abadiyeh), a Predynastic Settlement in Upper Egypt

      Bard, Kathryn A. (Department of Geosciences, The University of Arizona, 2003-01-01)
      In 1989 and 1991, wood charcoal samples were excavated at a Predynastic settlement in Upper Egypt, Halfiah Gibli (HG). A second site, Semaineh (SH), was also investigated, but as the ceramics there were mostly from the Old Kingdom, excavations were concentrated at HG. Wood charcoal was obtained in undisturbed contexts, in association with Nagada culture potsherds and lithics, ranging in date from about 3700 BC to 3200/3100 BC. These new radiocarbon dates provide more data for the relative phases of the Nagada culture, formulated mainly from ceramic seriation.
    • Radiocarbon Calibration for Japanese Wood Samples

      Sakamoto, Minoru; Imamura, Mineo; van der Plicht, Johannes; Mitsutani, Takumi; Sahara, Makoto (Department of Geosciences, The University of Arizona, 2003-01-01)
      The radiocarbon content of Japanese cedars was measured by accelerator mass spectrometry for decadal tree-ring samples from the period of 240 BC to AD 900. Conventional gas counting was also used for part of the samples. The data were compared with the INTCAL98 calibration curve (Stuiver et al. 1998). The results indicate that the difference in atmospheric 14C between Japan and North America or Europe is negligible at this period, less than 18 14C yr using an average of 50 yr. However, in the period of about AD 100 to about AD 200, we cannot exclude the possibility of a deviation of the order of 30 to 40 14C yr to the older ages.
    • Radiocarbon Age Offsets between Living Organisms from the Marine and Continental Reservoir in Coastal Localities of Patagonia (Argentina)

      Cordero, Robert R.; Panarello, Héctor; Lanzelotti, Sonia; Dubois, Cristian M. Favier (Department of Geosciences, The University of Arizona, 2003-01-01)
      The radiocarbon of the local reservoir effect (RE) was observed in many sectors along the Argentinean Patagonia coast. Results show variations in the 14C offsets and differences between marine and continental species growing within the same locality, ranging from about 80-1100 yr BP. It is postulated that such variations are mainly due to local factors, including the coast morphology and the contribution of continental waters. The relevance of these kinds of studies for the interpretation of age in archaeological samples is highlighted in this paper.
    • On the Coexistence of Man and Extinct Pleistocene Megafauna at Gruta del Indio (Argentina)

      García, Alejandro (Department of Geosciences, The University of Arizona, 2003-01-01)
      New excavations and new 14C dates at the Gruta del Indio shelter in the central Argentinean Andes show that the dung layer of the site is much thicker towards the front of the site than near the rock wall. This yields a longer chronology for the dung deposit; thus, the upper boundary would date to about 9000 14C yr BP. The new measurements lengthen the possible time of the coexistence of man and extinct Pleistocene megafauna in the area, since approximately 1400 cal yr is much longer than previously thought (Long et al. 1998). Nevertheless, coexistence does not imply interaction, which still is not evident.
    • Investigation of a Chinese Ink Rubbing by 14C AMS Analysis

      Yuan, Hong-Chien; Kutschera, Walter; Lin, Tze-Yue; Steier, Peter; Vockenhuber, Christof; Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2003-01-01)
      The date of a Chinese ink rubbing was determined using radiocarbon accelerated mass spectrometry (AMS) to be in the range from AD 1480 to AD 1670 (95.4% confidence limit). Together with a scanning electron microscope (SEM) analysis of the ink and a comparative study of the Chinese characters, it was determined that the ink rubbing must have been performed before Emperor Kang Hsi (AD 1662-1772), who ruled at the beginning of the Chin Dynasty. On the other hand, the stone stele, from which the ink rubbing was produced, was carved in AD 531, which is consistent with an analysis of some erased characters. Such analysis seems to be useful to help clarify possible forgeries of these art objects.
    • High-Precision AMS 14C Results on TIRI/ FIRI Turbidite

      Guilderson, Thomas P.; Southon, John R.; Brown, Thomas A. (Department of Geosciences, The University of Arizona, 2003-01-01)
      Unleached aliquots of TIRI/FIRI turbidite were analyzed by accelerator mass spectronomy (AMS) over a timespan of 18 months. Individual analyses ranged from 18,090-18,245 yr BP with reported errors between 30-50 yr. The weighted average fraction modern (FM) of these 28 measurements is 0.10378 +/0.00008 (which equates to 18,199 +/8 yr BP) and the measurements show a 1 standard deviation scatter of 0.00044 (+/35 yr). The fractional error of these results indicates reproducibility of individual measurements at the 4 per mil (1-sigma) level, which is consistent with the quoted counting-statistics-based errors. Laboratories engaged in the determination of 14C results at reasonably high precision should consider taking advantage of the TIRI and FIRI sample materials in the role of process standards. Additional suites of high-precision data are necessary to refine the accuracy of these sample materials.
    • El Mirón Cave and the 14C Chronology of Cantabrian Spain

      Straus, Lawrence Guy; González Morales, Manuel (Department of Geosciences, The University of Arizona, 2003-01-01)
      Excavations since 1996 in the large El Mirón Cave in the Cantabrian Cordillera of northern Spain have revealed a cultural sequence of late Mousterian, early Upper Paleolithic, Solutrean, Magdalenian, Azilian, Mesolithic, Neolithic, Chalcolithic, Bronze Age, and Medieval occupations. These components have been dated by 51 generally coherent radiocarbon determinations, all run by the Geochron labs, in association with the Lawrence Livermore labs for AMS. This series is one of the largest for a single prehistoric site in Iberia or even Europe. The series is consistent with the record from Cantabrian Spain and provides new detail on the age of the Middle-Upper Paleolithic transition, on the various phases of the Magdalenian culture, on the appearance of the Neolithic in the Atlantic zone of Spain, and on the origins of the socioeconomic complexity in the metal ages. The stratigraphic relationship of 14C-dated levels to a roof-fall block and adjacent cave walls (both with engravings) provides rare terminus post and ante quem ages for execution of the rupestral art in El Mirón during the early to mid Magdalenian. The 14C record has also been instrumental in revealing the existence of depositional hiati during the early Holocene.
    • Decadal Timescale Shift in the 14C Record of a Central Equatorial Pacific Coral

      Grottoli, A. G.; Gille, S. T.; Druffel, E. R. M.; Dunbar, R. B. (Department of Geosciences, The University of Arizona, 2003-01-01)
      Coral skeletal radiocarbon records reflect seawater Delta-14C and are useful for reconstructing the history of water mass movement and ventilation in the tropical oceans. Here, we reconstructed the inter-annual variability in central equatorial Pacific surface water Delta-14C from 1922-1956 using near-monthly 14C measurements in a Porites sp. Coral skeleton (FI5A) from the windward side of Fanning Island (3 degrees 54'32''N, 159 degrees 18'88''W). The most pronounced feature in this record is a large, positive shift in the Delta-14C between 1947 and 1956 that coincides with the switch of the Pacific Decadal Oscillation (PDO) from a positive to a negative phase in the mid-1940s. Although the absolute Delta-14C values from 1950-1955 in FI5A differ from the Delta-14C values of another coral core collected from the opposite side of the island, both records show a large, positive shift in their Delta-14C records at that time. The relative increase in the Delta-14C of each record is consistent with the premise that a common mechanism is controlling the Delta-14C records within each coral record. Overall, the Fanning Delta-14C data support the notion that a significant amount of subtropical seawater is arriving at the Equator, but does not allow us to determine the mechanism for its transport.
    • Dating of Prehistoric Burial Mounds by 14C Analysis of Soil Organic Matter Fractions

      Kristiansen, Søren M.; Dalsgaard, Kristian; Holst, Mads K.; Aaby, Bent; Heinemeier, Jan (Department of Geosciences, The University of Arizona, 2003-01-01)
      Dating of prehistoric anthropogenic earthworks requires either excavation for archaeological artifacts or macroscopic organic matter suitable for 14C analysis. Yet, the former, in many cases, is undesirable and the latter is difficult to obtain. Here we present a soil science procedure, which has the potential to overcome these problems. It includes careful sampling of buried former soil surfaces, acid-alkali-acid fractionation of soil organic matter (SOM), and subsequent 14C AMS dating. To test the procedure, soil from one of the largest known burial mounds in Scandinavia, Hohoj, and 9 other Danish burial mounds were sampled. The 14C dates from extracted SOM fractions were compared to reference ages obtained by other methods. We show that humic acid fractions in 7 of the 10 mounds had the same age as the reference, or were, at maximum, 280 yr older than the reference ages. The best age estimates were derived from an organic-rich layer from the upper cm of buried soil or sod. Differences among SOM fraction ages probably indicate the reliability of the dating. Hohoj dated to approximately 1400 BC and, thus, was up to 500 yr older than other dated Scandinavian mounds of comparable size. The remaining investigated burial mounds were dated to between 1700 and 1250 BC. We conclude that combined sampling of buried soil surfaces, SOM fractionation, and 14C analysis allows for dating of archaeological earthworks when minimal disturbance is required, or if no macroscopic organic remains are found.
    • Balanced Window Method in 14C Liquid Scintillation Counting

      Theodórsson, P.; Ingvarsdottir, S.; Gudjonsson, G. I. (Department of Geosciences, The University of Arizona, 2003-01-01)
      The authors present a detailed theoretical and experimental study of the liquid scintillation balanced counting method, widely used in radiocarbon dating, using a simple, laboratory-made system. A fixed counting window becomes a balanced window when the high voltage is set where the 14C count rate rises to a maximum. Using a measured 14C pulse height spectrum, we have calculated the lower and upper limits for 11 balanced windows of varying width and their respective counting efficiencies. Furthermore, we have studied: (1) theoretically and experimentally, the counting efficiency for up to a +/15% shift in pulse height from the balanced setting, (2), the change in pulse height due to temperature variations, (3), the long-time stability of the system, and (4), a method that allows a quick determination of the balance voltage for individual samples, using the Compton spectrum of 133Ba. The standard deviation for thirty 24-hr measuring periods for a 14C standard (190 Bq) was within the expected statistical error (0.03%).
    • 14C Chronology of Late Pleistocene-Holocene Events in the Nizhnee Priamurie (Southeast Russia)

      Bazarova, V. B.; Mokhova, L. M.; Orlova, L. A.; Klimin, M. A.; Gvozdeva, I. G. (Department of Geosciences, The University of Arizona, 2003-01-01)
      The Russian Far East is characterized by widespread peat bogs with a sufficiently thick peat accumulation. A series of radiocarbon dates from the studied peat bogs (in Lower Amur) were obtained. Analysis of these dates shows that the total peat formation in this territory began in the Late Pleistocene-Holocene (11,830 +/820, TIG-157; 9975 +/120, SOAN-4025). The rates of peat accumulation and the humidity index were counted. In addition, the botanical composition and degree of peat decomposition were defined. These data allow to study in more detail climate fluctuation and the 14C chronology of Holocene events in the region studied.
    • 14C Absolute Chronology of Pyramid III and the Dynastic Model at Pachacamac, Peru

      Michczyński, Adam; Eeckhout, Peter; Pazdur, Anna (Department of Geosciences, The University of Arizona, 2003-01-01)
      Pachacamac, covering an area of about 600 hectares (ha) near the Pacific shore, is one of the largest and most important archaeological sites in Peru. Most of the monumental adobe-made buildings of the later pre-Inca period (or Late Intermediate Period, about 10th-15th century AD) are so-called pyramids with ramps (the role of the ramps has been interpreted in different ways). Precise dating of the pyramids appears as a crucial step in defining the functions of Pachacamac in pre-Inca times. In this paper, we present the results obtained from 3 field campaigns at Pyramid III, one of the biggest buildings of the site. A total of 24 radiocarbon datasets from 4 different laboratories will help us to place the various steps of development of Pyramid III on a timescale, defined on the basis of the excavations. More absolute dates are available from another pyramid with ramps, which allow us to make comparisons and propose a new model of interpretation for the Pachacamac site during the Late Intermediate Period (LIP).