Now showing items 14019-14038 of 20719

    • Radio on the Farm

      McInnes, John W. (College of Agriculture, University of Arizona (Tucson, AZ), 1926-02)
    • 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.
    • Radiocarbon 1993 Price List

      Department of Geosciences, The University of Arizona, 1993-01-01
    • Radiocarbon 1994 Price List

      Department of Geosciences, The University of Arizona, 1993-01-01
    • Radiocarbon 1994 Price List

      Department of Geosciences, The University of Arizona, 1994-01-01
    • Radiocarbon Accelerator (AMS) Dates for the Epipaleolithic Settlement at Abu Hureyra, Syria

      Moore, A. M. T.; Gowlett, J. A. J.; Hedges, R. E. M.; Hillman, G. C.; Legge, A. J.; Rowley-Conwy, P. A. (American Journal of Science, 1986-01-01)
      The prehistoric settlement of Abu Hureyra in Syria was occupied in both the Epipaleolithic and Neolithic periods. It has provided significant evidence for changes in economy at the time of the inception of agriculture in southwest Asia. Twenty accelerator mass spectrometry (AMS) dates have been obtained to determine the duration of occupation of the Epipaleolithic settlement there and the precise age of samples of cereal grains and animal bones found within it. The results have demonstrated that the AMS technique can answer such questions because it dates exceedingly small samples with high precision. The dates indicate that the Epipaleolithic settlement was inhabited for about a millennium, from before 11,000 to nearly 10,000 BP, significantly longer than had been anticipated from study of the artifacts.
    • Radiocarbon Activity Measurements of Oolitic Sediments from the Persian Gulf

      Šilar, Jan (American Journal of Science, 1980-01-01)
      Radiocarbon activity of successive parts of Pleistocene and Holocene ooids and mollusk shells from the Persian Gulf, Kuwait, was measured. The inner part of the ooids showed the lowest activity and the cement between grains the highest. Radiocarbon activities correspond to the general stratigraphy and to the position of the sediments. Radiocarbon ages of Pleistocene sediments seem to be very low due to recrystallization of aragonite. Higher radiocarbon activity of cement indicates that atmospheric carbon dioxide was involved in the subaerial diagenetic process. The radiocarbon age of well-preserved mollusk shells seems to be lower than their allegedly Pleistocene geologic age.
    • Radiocarbon Activity Variation in Dated Tree Rings Grown in Mackenzie Delta

      Fan, C. Y.; Tie-Mei, Chen; Si-Xun, Y.; Kai-Mei, Dai (American Journal of Science, 1986-01-01)
      We measured the Delta-14C values in 57 rings (from AD 1824 to 1880) of a white spruce grown in Mackenzie Delta (68 degrees N, 130 degrees W), as part of our continuing study of the Delta-14C variation related to solar activities. The values exhibit a 10 per mil fluctuation with an 11-year periodicity anti-correlated with the solar activity cycle. We also measured the Delta-14C values in 6 rings (from AD 1940 to 1945). The abnormally high value in the 1943 ring may be due to two large solar flares occurring in 1942.
    • Radiocarbon Activity Variation in Dated Tree Rings Grown in Mackenzie Delta

      Fan, C. Y.; Tie-Mei, Chen; Si-Xun, Yun; Kai-Mei, Dai (American Journal of Science, 1983-01-01)
      Forty-five tree rings (1881-1925) were taken from a white spruce grown near Campbell River in Mackenzie Delta, Canada, for the measurement of 14C activity variation. Because of the narrowness of the rings, 2 and sometimes 3 rings were combined to yield a total of 21 specimens. The 14C content in these specimens was measured with a liquid scintillation-PM tube counter system of the History Department of Peking University. The data points exhibit a 10 per mil variation, anti-correlated with sunspot numbers. The physical implication is discussed.
    • Radiocarbon After Four Decades: An Interdisciplinary Perspective [Announcement]

      Department of Geosciences, The University of Arizona, 1994-01-01
    • Radiocarbon After Four Decades: An Interdisciplinary Perspective [Announcement]

      Department of Geosciences, The University of Arizona, 1994-01-01
    • Radiocarbon Age Anomalies in Land Snail Shells from Texas: Ontogenetic, Individual, and Geographic Patterns of Variation

      Goodfriend, Glenn A.; Ellis, G. Lain; Toolin, L. J. (Department of Geosciences, The University of Arizona, 1999-01-01)
      Accelerator mass spectrometric (AMS) radiocarbon analyses of live-collected, prebomb samples of shell carbonates of the land snails Rabdotus dealbatus and R. Alternatus from Texas were carried out to quantify the characteristic age anomalies of land snails from limestone areas. Age anomalies are similar for the two species; they average +700 yr and vary by +/180 yr (1 sigma) among samples. Serial analysis of 1 shell reveals a significant ontogenetic trend in 14C age anomalies, with older apparent ages (up to 1200 yr) in the apical part of the shell and younger and uniform ages in the last whorl. No trend in age anomalies was found across a broad range of rainfall conditions (from 300 to 1000 mm mean annual rainfall).
    • Radiocarbon Age Anomalies in Pre- and Post-Bomb Land Snails from the Coastal Mediterranean Basin

      Quarta, G.; Romaniello, L.; D'Elia, M.; Mastronuzzi, G.; Calcagnile, L. (Department of Geosciences, The University of Arizona, 2007-01-01)
      The shell carbonate of pre- and post-bomb samples of 2 species of terrestrial gastropods (Theba pisana and Cernuella virgata) sampled along the coast of Apulia, southern Italy, were dated using accelerator mass spectrometry and carbon stable isotopes were analyzed. The analyses show, for both species, significant anomalies in the radiocarbon age due to the possible presence of a 14C-depleted source of carbon in the formation of the shell aragonite. The magnitude of the age anomaly was quantified in the studied area to ~1000 14C yr.
    • Radiocarbon Age Anomalies in Shell Carbonate of Land Snails from Semi-Arid Areas

      Goodfriend, Glenn A. (American Journal of Science, 1987-01-01)
      Radiocarbon age anomalies, resulting from ingestion of old carbonate, were measured in shell carbonate of live-collected snails from arid and semi-arid areas of Israel and the West Bank. The age anomalies were found to be similar to those in land snails from other climatic regions and averaged ca 1600 yr in Trochoidea seetzeni, 2200 yr in Sphincterochila spp, 800 yr in Levantina sp, and 1700 yr in coastal dune species. The differences are associated with ecological differences among taxa. The uncertainties of the age anomalies average several hundred years within each group. This renders radiocarbon dates of late Holecene snails relatively imprecise, whereas it has almost no effect on the age uncertainties of relatively old samples (ie, those with large errors of measurement). Procedures for correction for fractionation are discussed.
    • Radiocarbon Age Assessment of a New, Near Background IAEA 14C Quality Assurance Material

      Hogg, A. G.; Higham, Thomas; Robertson, Steve; Beukens, Roelf; Kankainen, Tuovi; McCormac, F. G.; van der Plicht, Johannes; Stuiver, Minze (Department of Geosciences, The University of Arizona, 1995-01-01)
      The 14C Quality Assurance Programme coordinated by the IAEA (Rozanski  et al. 1992) prepared a set of five new intercomparison materials, including 40-50 ka old subfossil wood excavated from New Zealand peat bogs (IAEA C-4 standard). Statistical analysis of 79 14C measurements made on the wood indicated considerable variation in the results, with a marked skewness toward more modern values. The wide range of results and the possibility of inhomogeneity within the standard prompted the recovery and analysis of replacement material. The new subfossil wood sample is kauri (Agathis australis), at least 50 ka old, excavated from a swamp in Northland. It is in the form of a single plank, 6 m long, weighing 80 kg. It will be forwarded to the IAEA in Vienna for milling and distribution. Subsamples were obtained from both ends of the plank and analyzed by six laboratories. We present here the results of these analyses and compare them with the previous IAEA intercalibration results for the C-4 standard.
    • Radiocarbon Age Calibration Back to 13,300 Years BP and the 14C Age Matching of the German Oak and US Bristlecone Pine Chronologies

      Stuiver, Minze; Kromer, Bernd; Becker, Bernd; Ferguson, C. W. (American Journal of Science, 1986-01-01)
    • Radiocarbon Age Calibration of Marine Samples Back to 9000 Cal Yr BP

      Stuiver, Minze; Pearson, Gordon W.; Braziunas, Thomas F. (American Journal of Science, 1986-01-01)
    • Radiocarbon Age for the Cultural Layer of the Neolithic-Bronze Age Settlement Pesochnoe-1 (Lake Nero, Russia)

      Alexandrovskiy, A. L.; Voronin, K. V.; Dolgikh, A. V.; Kovalukh, N. N.; Skripkin, V. V.; Glavatskaya, E. V. (Department of Geosciences, The University of Arizona, 2012-10-15)
      Organic matter in the cultural layer of the ancient settlement Pesochnoe-1 near Lake Nero (NE of Moscow) yields reliable radiocarbon dates. The reason for this is the high concentrations of calcium and phosphorus in the cultural layer, especially in calcined bones. Several cultural epochs are distinguished in the cultural layer consisting of more or less homogeneous habitation deposits colored with humic susbstances. Artifacts of the Ljalovo culture are found in the lower part of the cultural layer; above these, artifacts of the Volosovo culture are present, and the upper part of the cultural layer corresponds to the Textile Ceramics culture. The 14C dates for humic substances in the layers show a good chronological stratification and correspond to known ages of these cultural stages. The 14C dates for the Ljalovo cultural layer cover 5600–5100 BP (4430–3900 cal BC), and dates for the Volosovo cultural layer span 4400–4200 BP (3000–2840 cal BC). Most dates from the upper part of the cultural layer correspond to the chronological interval of the Textile Ceramics culture and range from 3700 to 3200 BP (2100–1460 cal BC). More precise 14C dates were obtained for humic substances from archaeological objects in the upper cultural layer (hearths, fillings of pottery vessels, etc.): 3900–3500 BP (2100–1800 cal BC).
    • Radiocarbon Age of the Laacher See Tephra: 11,230 +/- 40 BP

      Hajdas, Irena; Ivy-Ochs, S. D.; Bonani, Georges; Lotter, André F.; Zolitschka, Bernd; Schlüchter, Christian (Department of Geosciences, The University of Arizona, 1995-01-01)
      The Laacher See Tephra (LST) layer provides a unique and invaluable time marker in European sediments with increasing importance because it occurs just before the onset of the Younger Dryas (YD) cold event. As the YD begins ca. 200 calendar years after the LST was deposited, accurate determination of the radiocarbon age of this ash layer will lead to a more accurate age assignment for the beginning of the YD. On the basis of 12 terrestrial plant macrofossil 14C ages derived from sediments from Soppensee, Holzmaar and Schlakenmehrener Maar, we found an age of at least 11,230 +/40 BP for the LST event. This is ca. 200 yr older than the often reported age of 11,000 +/50 BP (van den Bogaard and Schmincke 1985).
    • Radiocarbon Age of Vertisols and its Interpretation Using Data on Gilgai Complex in the North Caucasus

      Kovda, Irina; Lynn, Warren; Williams, Dewayne; Chichagova, Olga (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon dates were analyzed to assess Vertisols age around the world. They show an increase of radiocarbon age from mainly modern-3000 BP in 0-100 cm layer up to 10,000 BP at a depth 100-200 cm. Older dates reflect the age of parent material. The inversion of 14C dates seems to be a frequent phenomenon in Vertisols. A series of new dates of Vertisols from gilgai microhigh, microslope and microlow in the North Caucasus was done in order to understand the nature of this inversion. 14C age in the gilgai soil complex ranges from 70 +/45 BP in the microlow to 5610 +/180 BP in the microhigh. A trend of similar depths being younger in the microslope and microlow was found. We explain this by intensive humus rejuvenation in the microlows due to water downward flow. The older date in the microhigh represents the old humus horizon sheared laterally close to the surface and preserved by impermeable water regime. We explain inversions of 14C age-depth curves by the sampling procedures. In a narrow pit, genetically different parts of former gilgai could easily be as a genetically uniform soil profile. Because of this strong microvariability, Vertisols require sampling in a trench accounting for gilgai elements, even when gilgai are not obvious.