Radiocarbon, Volume 41 (1999): Recent submissions

Now showing items 41-45 of 45

    • AMS 14C Dating of Equipment from the Iceman and of Spruce Logs from the Prehistoric Salt Mines of Hallstatt
      Rom, Werner; Golser, Robin; Kutschera, Walter; Priller, Alfred; Steier, Peter; Wild, Eva M. (Department of Geosciences, The University of Arizona, 1999-01-01)
      This paper summarizes radiocarbon measurements of mainly botanical samples from the Iceman ("Otzi") and from his discovery site, an Alpine glacier at the Austrian-Italian border. The results were obtained by accelerator mass spectrometry (AMS) at 3 different laboratories (Vienna, Austria; Uppsala, Sweden; Gif-sur-Yvette, France) between 1992 and 1997. All the dates, except 2, are consistent with the time period 3360-3100 BC, as previously determined from bone and tissue samples from the Iceman himself. The 2 exceptional dates from wooden artifacts suggest that the site of the Iceman was used as a mountain pass for millennia prior to and after the lifetime of "Ötzi". For a 2nd sample complex, we studied logs from the beginning of salt mining in the world's oldest salt mines at Hallstatt in Upper Austria. 14C AMS measurements were performed in Vienna on spruce samples found in the prehistoric mines and from a log-house on the surface. Data evaluation included "wiggle matching" of different sets of tree rings. The results suggest that salt mining in the Hallstatt region took place in the 14th-13th century BC, well before the so-called Hallstatt period. We discuss in some detail the chemical pretreatment of the samples and the data evaluation. We also present a comprehensive survey of 14C dates available in the literature concerning both botanical remains from the vicinity of the Iceman and from the earliest salt mining in Hallstatt.

    • A Simple Method to Separate Pollen for AMS Radiocarbon Dating and Its Application to Lacustrine and Marine Sediments
      Mensing, Scott A.; Southon, John R. (Department of Geosciences, The University of Arizona, 1999-01-01)
      We present a simple method for manually separating pollen concentrates for radiocarbon accelerator mass spectrometry (AMS) dating using a mouth pipetting system. The required equipment is readily available from scientific equipment supply houses at minimal cost. Pollen samples from lake sediments required about 4 h of hand picking, whereas samples from marine sediments required about 8 h labor. Pollen dates from marine sediments were much older than expected. We are attempting to resolve whether this is due to contamination of the pollen or the presence of significant quantities of old reworked pollen. Pollen dates from lake sediments associated with Mazama Ash were consistent with other published ages; however, replicate dates on pollen samples from above the ash were consistently older than the surrounding sediment. Our results suggest that caution must be used when interpreting pollen dates if the potential for sediment reworking is present.

    • A Delta-R Correction Value for Samoa from Known-Age Marine Shells
      Phelan, Matthew B. (Department of Geosciences, The University of Arizona, 1999-01-01)
      A first-order Delta-R correction value for marine samples is presented based on 3 radiocarbon determinations of known-age marine shells from Samoa.

    • A 23-Year Retrospective Blind Check of Accuracy of the Copenhagen Radiocarbon Dating System
      Rasmussen, Kaare L.; Tauber, Henrik; Bonde, Niels; Christensen, Kjeld; Theodórsson, Páll (Department of Geosciences, The University of Arizona, 1999-01-01)
      A 23-yr record of the measuring accuracy of the Copenhagen radiocarbon dating laboratory has retrospectively been provided through a true blind test. A total of 92 samples of oak from old tree trunks were dated in the period 1971 to 1993 and their dendrochronological age determined independently. The 14C activity of the dendrochronological samples measured in the Copenhagen radiocarbon laboratory was compared to the activity of the tree rings of the same age measured by Stuiver and Pearson (1993) for calibration purposes. The average difference was found to be 54 +/72 14C yr. The results further indicate that the actual standard deviation is only 7% higher than that quoted by the laboratory. The investigation has shown a long-term stability of laboratory accuracy with no systematic laboratory variations either with respect to sample age or to the time of measurement from 1971 to 1993.

    • 14C Age of Glaciation in Estrecho de Magallanes–Bahía Inútil, Chile
      Heusser, C. J. (Department of Geosciences, The University of Arizona, 1999-01-01)
      Basal 14C dates from a core of the mire at Puerto del Hambre (53 degrees 36'21"S, 70 degrees 55'53"W), located within the area of glaciation in Estrecho de Magallanes-Bahia Inutil, Chile, are no older than 14,455 +/115 yr BP. The 14C dates are on samples from which screening isolated autochthonous plant remains. Previous 14C dates of 15,800 +/200, 16,590 +/320, and 16,290 +/140 yr BP are from bulk samples collected from similar basal increments at the site during 3 separate, independent coring operations. The previous suite of 14C dates was suspected to be contaminated by older carbon in the light of chronological evidence, which indicates a 14C age of approximately 14,850 yr BP for glaciation elsewhere in southern Chile. Contamination by "infinitely old" carbon reworked from nearby Tertiary beds and redeposited at Puerto del Hambre is evidently the cause for the older 14C dates.