• Organizing Committee & International Committee

      Department of Geosciences, The University of Arizona, 1995-01-01
    • From the Editor

      Long, Austin (Department of Geosciences, The University of Arizona, 1995-01-01)
    • Errata

      Department of Geosciences, The University of Arizona, 1995-01-01
    • Associate Editors

      Department of Geosciences, The University of Arizona, 1995-01-01
    • 3rd International Symposium

      Department of Geosciences, The University of Arizona, 1995-01-01
    • 1996 Price List

      Department of Geosciences, The University of Arizona, 1995-01-01
    • 16th International Radiocarbon Conference

      Department of Geosciences, The University of Arizona, 1995-01-01
    • The "Amsterdam Castle": A Case Study of Wiggle Matching and the Proper Calibration Curve

      van der Plicht, J.; Jansma, E.; Kars, H. (Department of Geosciences, The University of Arizona, 1995-01-01)
    • Subject Index Volume 37, Nos. 1 and 3, 1995

      Department of Geosciences, The University of Arizona, 1995-01-01
    • Spatial and Temporal Dependence of the 13C and 14C Isotopes of Wine Ethanols

      Martin, Gérard J.; Thibault, Jean-Noël (Department of Geosciences, The University of Arizona, 1995-01-01)
      More than 1000 authentic samples of ethanols were extracted by quantitative distillation from vintage wines and brandies prepared from grapes harvested in well-defined regions and years. The 13C contents of these ethanols were determined by isotope ratio mass spectrometry (IRMS) and the 14C activity of most of these samples was determined by liquid scintillation counting (ISC). We show that the 13C content of a C3 plant such as grape vine, which strongly depends on water availability, spans nearly a 10 per mil range worldwide. The efficiency of the 14C content of grape ethanols as a tracer of the CO2 turnover after the peak of the nuclear test in the 1960s is also discussed in terms of geographical effects. Finally, the necessity of a multi-isotopic approach, including 13C and 14C isotopes, for detecting sophisticated adulterations is illustrated in the case of wines and brandies.
    • Recent Reservoir ages for Danish Fjords and Marine Waters

      Heier, Nielsen Susanne; Heinemeier, Jan; Nielsen, H. L.; Rud, Niels (Department of Geosciences, The University of Arizona, 1995-01-01)
      AMS 14C dates were measured for 28 mollusk shells collected live in Danish waters over the period AD 1885 to 1945. Fourteen samples were from fjords and 14 were marine samples from the Danish Skagerrak-Kattegat coastal area and from the Belts. Reservoir ages were calculated for all samples on the basis of the tree-ring calibration curve. For the marine samples, which cover the period AD 1885-1916, we found a weighted-average reservoir age of 377 +/16 yr. The marine Delta-R values (the difference between the measured 14C age and the age deduced from marine, mixed-layer model calculation of Stuiver, Pearson and Braziunas (1986)) were found to be uniform within the experimental uncertainty with a weighted average of Delta-R = 13 +/16yr. Based on the observed scatter, the standard deviation is 21 yr. This result shows that it is justified to use the marine calibration curve with standard parameters (Delta-R = 0) when 14C-dating marine samples from the Danish area. Our value is consistent with the result Delta-R = -33 +/27 yr previously found for the Norwegian and Swedish Skagerrak-Kattegat coasts. In contrast, reservoir ages for Danish fjords were found to vary from 400 to >900 yr, far beyond experimental uncertainty. We ascribe this to varying content of dissolved, old soil carbonate (hard-water effect). Therefore, dating of samples from such fjord environments is expected to be uncertain by several hundred years.
    • Radiocarbon Updates

      Department of Geosciences, The University of Arizona, 1995-01-01
    • Radiocarbon in Tropospheric CO2 and Organic Materials from Selected Northern Hemisphere Sites

      Druffel, Ellen R. M.; Griffin, Sheila (Department of Geosciences, The University of Arizona, 1995-01-01)
      Radiocarbon was measured in atmospheric CO2 from La Jolla, California and in living organic materials from six sites in the northern hemisphere. Atmospheric CO2 Delta-14C values from La Jolla agreed with those previously published records from China Lake, California (Berger et al.1987) and Vermunt, Austria (Levin et al.1985). Delta-14C values of fruit and grain samples that grew during 1980 agreed with the atmospheric CO2 Delta-14Cmeasurements. Most of the Delta-14C results of fruit and corn samples stored since the 1940s agreed with tree-ring Delta-14C values for the same time period. In general, agreement was found between the atmospheric CO2 or tree-ring Delta-14C records available for the Northern Hemisphere and the Delta-14C signatures of rapidly exchanging organic matter pools examined in this study. Exceptions were the Delta-14C values of carbonate from egg shells and that of organic carbon from egg insides, which demonstrate that bicarbonate and organic carbon within the egg follow different biochemical pathways.
    • Palynological and Sedimentological Evidence for a Radiocarbon Chronology of Environmental Change and Polynesian Deforestation from Lake Taumatawhana, Northland, New Zealand.

      Elliot, M. B.; Striewski, B.; Flenley, J. R.; Sutton, D. G. (Department of Geosciences, The University of Arizona, 1995-01-01)
      We present pollen diagrams and sedimentological analyses from a lake site within an extensive dune system on the Aupouri Peninsula, Northland. Five thousand years ago, a regional Agathis australis — podocarp-broadleaf forest dominated the vegetation, which manifested an increasing preponderance of conifer species. Climate was cooler and drier than at present. From ca. 3400 BP, warmth-loving species such as A. Australis and drought-intolerant species, Dacrydium cupressinum and Ascarina lucida, became common, implying a warm and moist climate. The pollen record also suggests a windier climate. The most significant event in the record, however, occurred after ca. 900 BP (800 cal BP) when anthropogenic deforestation commenced. A dramatic decline in forest taxa followed, accompanied by the establishment of a Pteridium-esculentum-dominated community. Fire almost certainly caused this, evidenced by a dramatic increase of charcoal. Sedimentological evidence for this site indicates a relatively stable environment before humans arrived and an increasingly unstable environment with frequent erosional events after human contact.
    • On Cosmic-Ray Exposure Ages of Terrestrial Rocks: A Suggestion

      Lal, Devendra (Department of Geosciences, The University of Arizona, 1995-01-01)
      An important recent development in the field of geomorphology has been the application of in-situ cosmic-ray-produced nuclides to obtain model erosion rates and surface exposure ages. These concepts emerged some four decades ago in studies of cosmogenic nuclides in meteorites, but cannot generally be used analogously for terrestrial rocks. The differences in the two cases are outlined. For the case of steady-state erosional histories, the terrestrial surface exposure ages depend on the half-life of the radionuclide studied. A suggestion is made for presenting the surface exposure ages, which allows a clear definition of the meaning of the estimated exposure ages. In the case of a discrete exposure history, the meaning of "exposure age"—which should more appropriately be called "event age"—is however quite unambiguous.
    • Locating Archaeological Horizons with 14C Sediment Dating: The Case of the Lost City of Helike

      Maniatis, Yannis; Facorellis, Yorgos; Soter, Steven; Katsonopoulou, Dora; Kromer, Bernd (Department of Geosciences, The University of Arizona, 1995-01-01)
      In 373 BC a catastrophic earthquake and seismic sea wave destroyed Helike, a Greek city near Aigion on the southern shore of the Gulf of Corinth. The ruins were buried by sediments of unknown depth, leaving no trace of the city. We here discuss the radiocarbon dating of organic sediment samples recovered from seven boreholes drilled on the coastal plain in the area where ancient sources located Helike. Most of the samples apparently acquired a substantial addition of older carbon from natural sources, and hence their apparent ages are older than the true ages of sedimentation. However, if we assume that the addition is systematic, we can use the apparent ages to show that the sedimentation rate was initially rapid (about 1 cm yr-1) for the strata between 40 and 10 m below the surface, and then decreased by an order of magnitude about 6500 yr ago. A related change in the sediment deposition at about the same time has been found in many other marine deltas throughout the world, probably due to the deceleration of the global sea-level rise. We conclude that in the boreholes sampled by the present data, the horizon corresponding to ancient Helike is less than 8 m deep.
    • Improved Radiocarbon Age Estimation Using the Bootstrap

      Aczel, Amir D. (Department of Geosciences, The University of Arizona, 1995-01-01)
      This paper proposes the use of the statistical bootstrap technique as an aid in combining radiocarbon date estimates. The rationale for the use of the bootstrap is the theoretical result that, even if individual date estimates are normally distributed, their combination by the usual formula results in a random quantity that is not normal but rather a mixture of distributions. The bootstrap is a non-parametric, computer-intensive technique. This technique can better estimate the actual distribution of the combined age, leading to more precise confidence intervals. While the bootstrap cannot solve the multiple-intercepts problem in calibration, it can nonetheless lead to better estimates. The benefits of using the bootstrap are especially noticeable when sample sizes are small (as is the case in other applications of this technique).
    • Further Evidence of Changing Stability of the Atmosphere

      Hartwig, Sylvius (Department of Geosciences, The University of Arizona, 1995-01-01)