• A Direct Method to Measure 14CO2 Lost by Evasion from Surface Waters

      Billett, M. F.; Garnett, M. H.; Hardie, S. L. (Department of Geosciences, The University of Arizona, 2006-01-01)
      Recent methodological advances in the use of zeolite molecular sieves for measuring the isotopic signature of CO2 have provided the opportunity to make direct measurements of 14CO2 in various field situations. We linked a portable molecular sieve/pump/IRGA system to a floating chamber to demonstrate the potential of the method to quantify the isotopic signature (d13C and 14C) of CO2 lost by evasion (outgassing) from surface waters. The system, which was tested on a peatland stream in Scotland, involved 1) an initial period of scrubbing ambient CO2 from the chamber, 2) a period of CO2 build-up caused by surface water evasion, and 3) a final period of CO2 collection by the molecular sieve cartridge. The field test at 2 different sites on the same drainage system suggested that the results were reproducible in terms of d13C and 14C values. These represent the first direct measurements of the isotopic signature of CO2 lost by evasion from water surfaces.
    • 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.
    • AMS Radiocarbon Dating of Ancient Bone Using Ultrafiltration

      Higham, T. F. G.; Jacobi, R. M.; Bronk Ramsey, C. (Department of Geosciences, The University of Arizona, 2006-01-01)
      The Oxford Radiocarbon Accelerator Unit (ORAU) has used an ultrafiltration protocol to further purify gelatin from archaeological bone since 2000. In this paper, the methodology is described, and it is shown that, in many instances, ultrafiltration successfully removes low molecular weight contaminants that less rigorous methods may not. These contaminants can sometimes be of a different radiocarbon age and, unless removed, may produce erroneous determinations, particularly when one is dating bones greater than 2 to 3 half-lives of 14C and the contaminants are of modern age. Results of the redating of bone of Late Middle and Early Upper Paleolithic age from the British Isles and Europe suggest that we may need to look again at the traditional chronology for these periods.
    • An Early Holocene/Late Pleistocene Archaeological Site on the Oregon Coast? Comments on Hall et al. (2005)

      Moss, Madonna L.; Connolly, Thomas J.; Erlandson, Jon M.; Tasa, Guy L. (Department of Geosciences, The University of Arizona, 2006-01-01)
      In the journal Radiocarbon, Hall et al. (2005:383) claim that 35-CS-9, located in Bandon Ocean Wayside State Park on the southern Oregon coast, is one of the few Oregon coast sites that includes sediments and artifacts dating to the early Holocene and possibly to the late Pleistocene. Their claim for an early Holocene or late Pleistocene human occupation rests on a single radiocarbon date of 11,000 +/140 BP (12,710-12,680 cal BP) taken from charcoal found at least 20 cm below the nearest artifact. Although Hall et al. Compile various kinds of geoarchaeological evidence to support this claim, their case is not convincing. While we applaud aspects of their analyses, the inferences they have drawn are not substantiated by the evidence they present. We agree that 35-CS-9 is a significant site but believe claims for the antiquity of its human use have been exaggerated.
    • Book Review: Archaeology in Practice: A Student Guide to Archaeological Analyses, Jane Balme, Alistair Paterson (Eds.)

      Schiffer, M. B. (Department of Geosciences, The University of Arizona, 2006-01-01)
    • Climate in the Great Lakes Region Between 14,000 and 4000 Years Ago from Isotopic Composition of Conifer Wood

      Leavitt, Steven W.; Panyushkina, Irina P.; Lange, Todd; Wiedenhoeft, Alex; Cheng, Li; Hunter, R. Douglas; Hughes, John; Pranschke, Frank; Schneider, Allan F.; Moran, Joseph; et al. (Department of Geosciences, The University of Arizona, 2006-01-01)
      The isotopic composition of ancient wood has the potential to provide information about past environments. We analyzed the d13C, d18O, and d2H of cellulose of conifer trees from several cross-sections at each of 9 sites around the Great Lakes region ranging from ~4000 to 14,000 cal BP. Isotopic values of Picea, Pinus, and Thuja species seem interchangeable for d18O and d2H comparisons, but Thuja appears distinctly different from the other 2 in its d13C composition. Isotopic results suggest that the 2 sites of near-Younger Dryas age experienced the coldest conditions, although the Gribben Basin site near the Laurentide ice sheet was relatively dry, whereas the Liverpool site 500 km south was moister. The spatial isotopic variability of 3 of the 4 sites of Two Creeks age shows evidence of an elevation effect, perhaps related to sites farther inland from the Lake Michigan shoreline experiencing warmer daytime growing season temperatures. Thus, despite floristic similarity across sites (wood samples at 7 of the sites being Picea), the isotopes appear to reflect environmental differences that might not be readily evident from a purely floristic interpretation of macrofossil or pollen identification.
    • Coastal Upwelling and Radiocarbon—Evidence for Temporal Fluctuations in Ocean Reservoir Effect off Portugal During the Holocene

      Monge Soares, António; Alveirinho Dias, João M. (Department of Geosciences, The University of Arizona, 2006-01-01)
      This paper focuses on the use of the radiocarbon content of marine shells collected along the Portuguese coast as a proxy for the intensity of coastal upwelling off of Portugal. Differences in the 14C ages of closely associated marine mollusk shells and terrestrial material (charcoal or bones) from several Portuguese archaeological contexts seem to be significant throughout the Holocene. Delta-R values range from 940 +/50 to 160 +/40 14C yr. Five of these values are significantly higher than the modern value (250 +/25 14C yr), while the remaining values are lower. The modern value was calculated by measuring the 14C content of live-collected, pre-bomb marine mollusk shells. This value is in accordance with an active upwelling of strong intensity that currently occurs off of Portugal. Some primary observations based on data presented here can be made: i) during the Holocene important changes have occurred in the ocean reservoir effect off the Portuguese coast; ii) these fluctuations may be correlated with regional oceanographic changes, namely with changes in the strength of coastal upwelling; and iii) these changes suggest some sort of variability of the climatic factors forcing coastal upwelling off of Portugal.
    • Comment On “Diet-Derived Variations in Radiocarbon and Stable Isotopes: A Case Study from Shag River Mouth, New Zealand”

      Beavan Athfield, Nancy (Department of Geosciences, The University of Arizona, 2006-01-01)
    • Comments on Sveinbjörnsdóttir et al. (2004) and the Settlement of Iceland

      Olsson, Ingrid U. (Department of Geosciences, The University of Arizona, 2006-01-01)
      Radiocarbon dates on samples aimed to date the settlement of Iceland are given together with comments by the laboratory, since many of the results and descriptions given by Sveinbjörnsdóttir et al. (2004) in Radiocarbon, together with new results, are in error. The intention of this paper is to present correct dates and further relevant information regarding samples used earlier and to discuss possible complications inherent in the method of Sveinbjörnsdóttir et al. (2004). Examples are given of how critical the collection, treatment, and interpretation of samples may be. An age difference between birch charcoal and grains for a site is expected due to various reasons. If the difference amounts up to ~100 yr, as reported by Sveinbjörnsdóttir et al. (2004), it must only to a small degree be due to biological age. Reference to an excavation report, details regarding stratigraphy, and discussions of the risk for displacement and contamination are missing in their paper. A final evaluation of the time for settlement should not be done until more research is completed and other possible or earlier suggested or even dated sites are discussed. A summary is given of the research on the island and volcanic effects on the 14C activity of the atmospheric CO2, especially over Iceland.
    • Dating Paleosol and Animal Remains in Loess Deposits

      Zhang, H. C.; Li, B.; Yang, M. S.; Lei, G. L.; Ding, H.; Niu, Jie; Fan, H. F.; Zhang, W. X.; Chang, F. Q. (Department of Geosciences, The University of Arizona, 2006-01-01)
      Accurate and reliable dating of paleosols, animal remains, and artifacts is of crucial importance in reconstructing environmental change and understanding the interrelationship between human activities and natural environments. Dating different materials in the same sample can help resolve problems such as soil carbon sources and carbon storage state. Conventional radiocarbon dating of soil (inorganic and organic matter) and accelerator mass spectrometry (AMS) dating of animal remains (fossil bones and teeth) result in different ages for materials from the same sample position in a typical loess section at Xinglong Mountain, Yuzhong County, Gansu Province in NW China. Inorganic matter is ~3400 yr older than organic matter, 4175 +/175 cal BP to 3808 +/90 cal BP. A 1610-yr difference between the 14C ages of fossils (animal bones and teeth) and soil organic matter suggests that a depositional hiatus exists in the studied profile. The varying 14C ages of fossils and soil organic and inorganic matter have important implications for paleoclimate reconstructions from loess sections. It is critical to consider the meaning of the variable 14C ages from different material components from the same sample position in terms of soil organic and inorganic carbon storage, vegetation history reconstruction, archaeology, and the study of ancient civilizations.
    • Determination of 90Sr/90Y in Wheat Grains, Soil, and Deposition Samples by TBP Extraction and Cerenkov Counting

      Gertmann, Udo Ch; Tschöpp, Vlasta (Department of Geosciences, The University of Arizona, 2006-01-01)
      Within the framework of radioecological studies, 90Sr was determined in wheat grains, soil, and deposition samples. The radiochemical purification of 90Y consisted of liquid-liquid extraction by tributyl phosphate (TBP), followed by hydroxide and oxalate precipitations and, if necessary, the removal of thorium by anion exchange chromatography. The procedure proved to be very robust and reliable, having yttrium yields of 92.7 4.6% for 1-kg wheat samples, 90.9 4.2% for 50-g soil samples, and 90.6 3.2% for wet and dry deposition samples. 90Y was determined by Cerenkov counting and proportional counting. By optimizing the Cerenkov counting window, a figure of merit (FOM) of 4750 could be reached using a Quantulus 1220 system. Minimum detectable activities were in the range of 10 mBq.
    • Dilemma of Dating on Lacustrine Deposits in an Hyperarid Inland Basin of NW China

      Zhang, H. C.; Ming, Q. Z.; Lei, G. L.; Zhang, W. X.; Fan, H. F.; Chang, F. Q.; Wünnemann, B.; Hartmann, K. (Department of Geosciences, The University of Arizona, 2006-01-01)
      Conventional and accelerator mass spectrometry (AMS) radiocarbon, TL, OSL, and IRSL dating results on samples from the cores D100 and I70 from Ejina Basin, one of the most important inland basins in arid-hyperarid NW China, show that it is difficult to determine the ages of sediments at different depths. AMS ages of core D100 samples demonstrate that the sediments at depths from 10 to 90 m were formed between 14 to 30 kyr BP. The inverted ages from both the D100 and I70 cores imply that there was a strong reworking of the sediments during and after deposition processes. The inverted ages also indicate drastic fluctuations of groundwater bearing soluble organic matters, which might be related to neotectonic activities and climate changes during the period. Consequently, it is impossible to establish an accurate and reliable chronology for the cores based only on these dates. All AMS ages, if they are reliable and acceptable, indicate a high deposition rate (5~8 mm/yr), and since all TL, OSL, and IRSL ages are much older than those given by AMS, it makes these methods questionable for determining the ages of lacustrine-fluvial-alluvial deposits.
    • ENEA Radiocarbon Measurements I

      Magnani, Giuseppe; Bartolomei, Paolo; L, Teresa; Marino, Ernesto Claudio; Govoni, Claudio (Department of Geosciences, The University of Arizona, 2006-01-01)
      This paper includes determinations of archeological and geological samples from different sites in central Italy performed at the Ente per le Nuove Tecnologie l'Energia e l'Ambiente (ENEA) Radiocarbon Laboratory. This laboratory has been in operation since 1985 at the ENEA Bologna Research Center.
    • 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.
    • Erratum

      Department of Geosciences, The University of Arizona, 2006-01-01
      There is an error in the previous issue of Radiocarbon.
    • 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.
    • 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.
    • In Memoriam: Henry N. Michael (1912-2006)

      Department of Geosciences, The University of Arizona, 2006-01-01
    • 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.