• The International Radiocarbon Data Base: A Progress Report

      Kra, Renee S. (Department of Geosciences, The University of Arizona, 1989-01-01)
      An International Radiocarbon Data Base (IRDB), an online centralized 14C data management and retrieval system has been designed and established to compile, edit and disseminate data to researchers in many scientific fields. The need for such a research tool has been apparent for some years. Since 1985, planning conferences and workshops have addressed the issues of implementing the IRDB. Workshops in Groningen and, most recently in New Haven, have led to consensus on a microcomputer-driven catalogue-type data retrieval management system, selection of an American Advisory Board and the initiation of two pilot projects. A permanent home has been found for the data base at The University of Arizona. It is hoped that our efforts toward international cooperation will culminate with the official launching of this much needed, long overdue enterprise.
    • Dating of the Upper Pleistocene Lithic Industry of Sardinia

      Hofmeijer, G. Klein; Alderliesten, C.; van der Borg, Klaas; Houston, C. M.; De Jong, A. F. M.; Martini, F.; Sauges, M.; Sondaar, P. Y.; De Visser, J. A. (Department of Geosciences, The University of Arizona, 1989-01-01)
      During an excavation of 1986 and 1987, a joint team from Utrecht, Siena and the Soprintendenza di Sassari a Nuoro, found a pre-Neolithic lithic industry in Corbeddu Cave, Oliena, Sardinia, which was dated to 8000-17,000 BP. The artifact typology is different from that of the mainland of the same period. The lithic and bone artifacts suggest an endemic isolated economy of the Upper Pleistocene in Sardinia.
    • The Recovery and Dating of Carbon Dioxide in Polar Ice Cores

      Wilson, A. T.; Donahue, Douglas J. (Department of Geosciences, The University of Arizona, 1989-01-01)
      A new method is described for recovering trapped CO2 from polar ice cores. The ice is sublimed under vacuum, and H2O vapor and CO2 are collected at appropriate cold traps. The application of this method to obtain CO2 from a specific ice core, the conversion of that CO2 to graphite, and the measurement of radiocarbon in the CO2 are described in detail. The potentialities and problems of the method are discussed.
    • The Role of 36Cl and 14C Measurements in Australian Groundwater Studies

      Bird, J. R.; Calf, G. E.; Davie, R. F.; Fifield, L. K.; Ophel, T. R.; Evans, W. R.; Kellett, J. R.; Habermehl, M. A. (Department of Geosciences, The University of Arizona, 1989-01-01)
      An Accelerator Mass Spectrometry system has been developed using the 14UD tandem accelerator at the Australian National University. It has been used for 36Cl measurements on groundwater samples from the Murray Basin in southeastern Australia. Measurements of 14C have also been made on the same groundwaters. The information can be combined with stable isotope ratios and other data to illustrate the occurrence of processes such as radioactive decay and local recharge in different aquifers.
    • Early English Boats

      Switsur, Roy (Department of Geosciences, The University of Arizona, 1989-01-01)
      A large number of early boats discovered in the waterways of England are presently displayed in museums and as public monuments. In some cases conservation practices have caused problems in the radiocarbon dating of these otherwise undated artifacts. Specimen pretreatments are described and the chronology of the boats in different regions of England are presented with approximate calibration to calendar date ranges.
    • Design and Preparation of Samples for the International Collaborative Study

      Harkness, D. D.; Cook, G. T.; Miller, B. F.; Scott, E. M.; Baxter, M. S. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Sample materials issued to participants in the interlaboratory calibration exercise are defined and in context of their intended interpretational significance. Preparation of the benzene and calcium carbonate standards as issued for stage 1 is described in detail; likewise, the source and pretreatment/extraction of the environmental samples dispatched for stages 2 and 3.
    • Determination of 14C in Alcoholic Beverages

      Schonhofer, Franz (Department of Geosciences, The University of Arizona, 1989-01-01)
      A simple and quick method for the determination of 14C in ethanol has been developed, using an ultra low-level liquid scintillation counter. I have studied factors influencing the lower limit of detection and have shown that liquor can be measured directly without pretreatment. Results of measurements on Austrian wines are presented and compared with results obtained from tritium measurements. The applicability and limitations of the results to age determination are discussed.
    • Evaluation of 14C Ages of Organic Fractions of Paleosols from Loess Paleosol Sequences Near Xian, China

      Head, M. J.; Zhou, Weijian; Zhou, Mingfu (Department of Geosciences, The University of Arizona, 1989-01-01)
      The 14C dating of organic fractions from paleosol layers containing <2% carbon in loess-paleosol sequences from the loess plateau in China has yielded results that are quite often much younger than the true age of the sediments. Percolation of modern organic materials from agricultural activities, and binding of these materials within the weathered clays of the paleosols has meant that conventional pretreatment techniques for 14C dating would not isolate a reliable chemical fraction. The total sequence from Bei Zhuang Cun, in Shaanxi Province, reflects the climatic history of the area for ca 30,000 years, ranging from the interstadial of the last glacial period to the postglacial period. Analysis of solvent extracts of organic material from this site indicates that they are mainly composed of carbohydrate residues originating from the relatively recent agricultural activity. Validity of the humic components for dating will be discussed.
    • Depth Profiles of Nitrogen and Chlorine in Pure Materials Through AMS of the Neutron Activation Products 14C and 36Cl

      Elmore, David; Hossain, T. Z.; Gove, H. E.; Hemmick, T. K.; Kubik, P. W.; Jiang, Songsheng; Lavine, J. P.; Lee, S. T. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Determination of the more common light elements such as nitrogen and chlorine at trace levels is difficult because of their high abundance on sample surfaces, in materials used to build analysis instruments, and in the residual gas of the instrument vacuum. We present here a new approach to analysis of these elements: accelerator mass spectrometry (AMS) combined with neutron activation. The problem of contamination is overcome by using neutron activation to produce long-lived radioisotopes which generally have low concentrations in the environment. For measurement of 14N and 35Cl, AMS can provide sensitive background-free measurements of their neutron activation products 14C and 36Cl and, in addition, can provide depth profiles. These are the first results of this new method: depth profiles of nitrogen and chlorine implanted in semiconductor grade silicon.
    • A Semi-Automated Bone Pretreatment System and the Pretreatment of Older and Contaminated Samples

      Law, I. A.; Hedges, R. M. (Department of Geosciences, The University of Arizona, 1989-01-01)
      A semi-automated continuous-flow system used to process archaeological bone to purified gelatin or amino acids for 14C dating is described. Powdered bone is retained in flow cells specifically designed to permit the sequential leaching of the bone with acid, alkali and water. Crude collagen obtained by this process is gelatinized, and than either purified directly using a macroporous cation exchange resin (BioRad AGMP-50), or hydrolyzed and the amino acids desalted on BioRad 50W-X8 resin. When compared with previous methods used by the laboratory, the new method allows more samples to be treated to a higher degree of purification. Examples of dates obtained on "standard" bones are presented, and confirm that no contamination is introduced from the components used in the new process.
    • Sources of Carbon to Deep-Sea Corals

      Griffin, Sheila; Druffel, Ellen R. M. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Radiocarbon measurements in deep-sea corals from the Little Bahama Bank were used to determine the source of carbon to the skeletal matrices. Specimens of Lophelia, Gerardia, Paragorgia johnsoni and Corallium noibe were sectioned according to visible growth rings and/or stem diameter. We determined that the source of carbon to the corals accreting organic matter was primarily from surface-derived sources. Those corals that accrete a calcerous skeleton were found to obtain their carbon solely from dissolved inorganic carbon (DIC) in sea water from the depth at which the corals grew. These results, in conjunction with growth-rate studies using short-lived radioisotopes, support the use of deep-sea corals to reconstruct time histories of transient and non-transient tracers at depth in the oceans.
    • AMS 14C Dating on the Fossvogur Sediments, Iceland

      Andersen, G. J.; Heinemeier, Jan; Nielsen, H. L.; Rud, Niels; Thomsen, M. S.; Johnsen, Sigfús; Sveinbjörnsdóttir, Árný E.; Hjartarson, Árni (Department of Geosciences, The University of Arizona, 1989-01-01)
      Several new AMS 14C dates on shells from the Fossvogur sea sediments in southern Iceland are reported. Up till now, researchers have assumed that the Fossvogur sediments formed during the last interglacial period (Eem), some 100,000 years ago. However, a recent 14C determination from this location yielded an age of ca 11,000 yr. Because of the importance of these sediments for the Quaternary chronology of Iceland, further sampling for 14C dating was subsequently initiated. The present results on several shell samples collected from the Fossvogur layers strongly indicate that these sediments were formed during the warm Allerød period toward the end of the last glaciation.
    • Carbon Uptake in Aquatic Plants Deduced from Their Natural 13C and 14C Content

      Marčenko, Elena; Srdoč, Dušan; Golubić, Stjepko; Pezdič, Jože; Head, M. J. (Department of Geosciences, The University of Arizona, 1989-01-01)
      delta-13C and 14C activity measurements were made on terrestrial, marsh and aquatic plants growing in their natural habitat of the Plitvice Lakes in northwest Yugoslavia. delta-13C values were ca -47 per mil for aquatic mosses, which indicate that the carbon source was dissolved inorganic carbon (DIC) from alkaline karst waters, following a C3 pathway, and ca -25 per mil for marsh plants, indicating the carbon source was atmospheric CO2. 14C activity of true aquatic plants and submerged parts of helophytes was close to 14C activity of DIC, whereas that of emergent parts of helophytes and terrestrial plants was similar to atmospheric CO2 activity. Aquatic plants which use DIC in freshwater for their photosynthesis are not suitable for 14C dating, unless the initial activity of incorporated carbon is known. delta-13C values of plant material also depend on the carbon source and cannot be used for 14C age correction.
    • North American Archaeologist

      Department of Geosciences, The University of Arizona, 1989-01-01
    • Carbon Isotope Dynamics in Some Tropical Soils

      Becker-Heidmann, Peter; Scharpenseel, Hans-Wilhelm (Department of Geosciences, The University of Arizona, 1989-01-01)
      We determined delta-13C and D14C in some agricultural soil profiles of the tropics: Ustaif from the semi-arid tropics (India), a Udult, an Aquoll and an Aquept from the humid tropics (Philippines). We used a thin-layer sampling, resulting in high-resolution depth-distribution patterns of natural 13C and 14C content of organic carbon. Regular plowing or puddling leads to uniform isotope concentrations in the topsoil. Decomposition of organic matter raises the delta-13C value, and vertical translocation raises the delta-13C value with depth. The change of cultivation from pulses (C3-type metabolism of photosynthesis) to sorghum (C4) results in a decrease of delta-13C with depth in the topsoil. Where the clay content in the subsoil is high, delta-13C remains constant, due to fixation of organic carbon to clay minerals, and D14C decreases with depth. Below the clay-enriched zone, delta-13C declines and D14C rises again, due to a chromatographic-like effect. At some horizon boundaries, inhomogeneities in texture delay percolation locally, thus preventing sorption and causing peak values of D14C.
    • The Geochemistry and Evolution of Natural Organic Solutes in Groundwater

      Wassenaar, Leonard Irwin; Aravena, Ramon; Fritz, Peter (Department of Geosciences, The University of Arizona, 1989-01-01)
      This paper describes the organic carbon cycle of the recharge environment of a shallow, sandy aquifer, with an emphasis on the origin, flux and geochemical evolution of dissolved organic carbon using liquid chromatography, carbon isotopes and GC-MS techniques. The two components of DOC investigated are hydrophobic acids and C1-C10 hydrophilic compounds. The 14C activity of these components of the DOC was measured using TAMS. 14C analyses of DOC components may provide an additional tool for groundwater dating. The initial 14C activity of DOC in a recharge zone, however, depends mainly on the residence times and cycling of DOC sources in the recharge environment. Using 14C DOC to estimate groundwater residence times between sampling points along a flow path compares well with residence times estimated on the basis of hydraulic parameters ark 14C DIC under closed system conditions.
    • The Continental European Suess Effect

      Levin, Ingeborg; Schuchard, Joachim; Kromer, Bernd; Münnich, K. O. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Observations of 14C in atmospheric CO2 at four different sites in central Europe, Heidelberg, Westerland, Schauinsland and Jungfraujoch have enabled us to determine individual fossil-fuel contributions to atmospheric CO2 concentration. The data clearly show a decrease of fossil-fuel CO2 with distance from anthropogenic source regions. At Heidelberg during winter we observe 14C/12C ratios up to 10% lower than at the clean air mountain station Jungfraujoch in the Swiss Alps, corresponding to an anthropogenic CO2 contamination level of ca 10% at the Heidelberg site. The Schauinsland and Westerland winter fossil-fuel CO2 concentrations are only ca 1.5 and 2% of the mean concentration, respectively. Our results indicate a strong seasonality in the European fossil-fuel CO2 source with ca 50% lower CO2 emissions during summer if compared to winter fossil-fuel CO2 release. This effect may significantly contribute (by 1-2 ppm) to the observed annual cycle of atmospheric CO2 concentration in northern mid-latitudes.
    • Aridity in Equatorial Africa During the Last 225,000 Years: A Record of Opal Phytoliths/ Freshwater Diatoms from the Zaire (Congo) Deep-Sea Fan (Northeast Angola Basin)

      Jansen, J. F.; Alderliesten, C.; Houston, C. M.; De Jong, A. F. M.; van der Borg, Klaas; Van Iperen, J. M. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Maps of accumulation rates of freshwater diatoms and opal phytoliths in the surface sediments of the Zaire fan show that both types of microfossils were supplied to the ocean floor by the Zaire River, and that opal phytoliths also have a southern source, probably the region of the Namibian desert. The PhFD ratio, of opal phytoliths to freshwater diatoms, can be regarded as an aridity index for equatorial Africa, and probably for large parts of the central and southern Atlantic. In two cores, the record of the PhFD ratio indicates humidity ca 225-190 ka BP, aridity 190-135 ka BP with maxima ca 170 and 140 ka BP and a humid excursion 150 ka BP, an increase in humidity 115 ka BP, a less humid period 90-30 ka BP, more humidity ca 30-17 ka BP with possibly more arid intervals ca 22.5 and 20 ka BP. In general, glacial (sub) stages were more arid and interglacial (sub) stages more humid. For the last 20 ka, the PhFD ratio corresponds closely with the known climatic events in tropical Africa.
    • Radiocarbon Dating with the Quantulus in an Underground Counting Laboratory: Performance and Background Sources

      Kalin, Robert M.; Long, Austin (Department of Geosciences, The University of Arizona, 1989-01-01)
      The University of Arizona Radiocarbon Laboratory purchased a state-of-the-art LKB Quantulus LSC and placed it into a new underground counting chamber. We have investigated the performance of the Quantulus in this setting comparing different vial types, checking background sources and experimenting with sample size.