• 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.
    • Change of Diet of the Greenland Vikings Determined from Stable Carbon Isotope Analysis and 14C Dating of Their Bones

      Arneborg, Jette; Heinemeier, Jan; Lynnerup, Niels; Nielsen, Henrik L.; Rud, Niels; Sveinbjörnsdóttir, Árny E. (Department of Geosciences, The University of Arizona, 1999-01-01)
      Bone samples from the Greenland Viking colony provide us with a unique opportunity to test and use 14C dating of remains of humans who depended upon food of mixed marine and terrestrial origin. We investigated the skeletons of 27 Greenland Norse people excavated from churchyard burials from the late 10th to the middle 15th century. The stable carbon isotopic composition (delta-13C) of the bone collagen reveals that the diet of the Greenland Norse changed dramatically from predominantly terrestrial food at the time of Eric the Red around AD 1000 to predominantly marine food toward the end of the settlement period around AD 1450. We find that it is possible to 14C-date these bones of mixed marine and terrestrial origin precisely when proper correction for the marine reservoir effect (the 14C age difference between terrestrial and marine organisms) is taken into account. From the dietary information obtained via the delta-13C values of the bones we have calculated individual reservoir age corrections for the measured 14C ages of each skeleton. The reservoir age corrections were calibrated by comparing the 14C dates of 3 highly marine skeletons with the 14C dates of their terrestrial grave clothes. The calibrated ages of all 27 skeletons from different parts of the Norse settlement obtained by this method are found to be consistent with available historical and archaeological chronology. The evidence for a change in subsistence from terrestrial to marine food is an important clue to the old puzzle of the disappearance of the Greenland Norse, obtained here for the first time by measurements on the remains of the people themselves instead of by more indirect methods like kitchen-midden analysis.
    • Changes in 14C Activity over Time During Vacuum Distillation of Carbon from Rock Pore Water

      Davidson, G. R.; Yang, I. C. (Department of Geosciences, The University of Arizona, 1999-01-01)
      The radiocarbon activity of carbon collected by vacuum distillation from a single partially saturated tuff began to decline after approximately 60% of the water and carbon had been extracted. Disproportionate changes in 14C activity and delta-13C during distillation rule out simple isotopic fractionation as a causative explanation. Additional phenomena such as matrix diffusion and ion exclusion in micropores may play a role in altering the isotopic value of extracted carbon, but neither can fully account for the observed changes. The most plausible explanation is that distillation recovers carbon from an adsorbed phase that is depleted in 14C relative to DIC in the bulk pore water.
    • Editorial Board

      Department of Geosciences, The University of Arizona, 1999-01-01
    • From the Editor

      Long, Austin (Department of Geosciences, The University of Arizona, 1999-01-01)
    • From the Managing and Associate Managing Editors

      Sewell, David; Elliott, Kimberley (Department of Geosciences, The University of Arizona, 1999-01-01)
    • 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 Calibration by the Date Distribution Method

      Muzikar, Paul (Department of Geosciences, The University of Arizona, 1999-01-01)
      A method is presented for calibrating radiocarbon ages based on statistical analysis of a large number of randomly distributed dates. One interesting feature of this method is that it is internal; that is, it allows one to extend a known calibration curve further back in time by using only 14C dates, with no reference to any other dating technique. A serious difficulty in implementing this method lies in assembling a sample of dates with the correct statistical properties.
    • Radiocarbon Dating of "Old" Charcoal Using a Wet Oxidation, Stepped-Combustion Procedure

      Bird, M. I.; Ayliffe, L. K.; Fifield, L. K.; Turney, C. M.; Cresswell, R. G.; Barrows, T. T.; David, B. (Department of Geosciences, The University of Arizona, 1999-01-01)
      We present results that validate a new wet oxidation, stepped-combustion procedure for dating "old" charcoal samples. An acid-base-wet oxidation (ABOX) pretreatment procedure has been developed that is used in place of the conventional acid-base-acid (ABA) pretreatment. Combustions and graphitizations are performed in a vacuum line that is insulated from the atmosphere by a second backing vacuum to eliminate the risk of atmospheric leakage into the line at any stage of the procedure. Combustions are performed at 3 temperatures (330 degrees C, 630 degrees C and 850 degrees C) with a graphite target produced from the CO2 evolved during each combustion step. In this way, the removal of any contamination can be monitored, and a high degree of confidence can be placed on the final age. The pretreatment, combustion, graphitization, and measurement blank for the procedure, based on the analysis of a "radiocarbon-dead" graphite, is 0.5 +/0.5 micrograms C (1sigma, n = 14), equivalent to 0.04 +/0.02 pMC or an "age" of approximately 60 ka for a 1 mg graphite target. Analyses of a "radiocarbon-dead" natural charcoal after ABOX pretreatment and stepped combustion suggest that the total blank (including contamination not removed by pretreatment) may be higher than for graphite, ranging up to 0.10 +/0.02 pMC. Additional experiments confirm good agreement with accepted values for the international low14C "New Kauri" standard (0.16-0.25 pMC). They also confirm excellent reproducibility, with 3 separate dates on different aliquots of a charcoal sample from Ngarrabullgan Cave (Queensland, Australia) ranging from 35.2 to 35.5 ka 14C BP. It is also demonstrated that the ABOX pretreatment, in conjunction with the new vacuum line described here, is able to remove contamination not removed by the conventional ABA pretreatment, suggesting that the technique can be used to produce reliable 14C dates on charcoal up to at least 50 ka.
    • Radiocarbon, Volume 41, Number 2 (1999)

      Department of Geosciences, The University of Arizona, 1999-01-01
    • Reliability of Bone Gelatin AMS Dating: Rattus exulans and Marine Shell Radiocarbon Dates from Pauatahanui Midden Sites in Wellington, New Zealand

      Athfield, Nancy Beavan; McFadgen, Bruce; Sparks, Rodger (Department of Geosciences, The University of Arizona, 1999-01-01)
      A suite of 6 bone gelatin accelerator mass spectrometry (AMS) radiocarbon dates for Rattus exulans Peale and associated beta decay 14C dates for Austrovenus stutchburyi shell are presented for 4 middens at Pauatahanui, Wellington, New Zealand. Mean calibrated age ranges of Rattus exulans (520-435 BP and 350-330 BP at 95% confidence level) and shell (465-375 BP at 95% confidence level) from the 4 midden sites overlap. The agreement between Rattus exulans bone gelatin dates and associated shell provides an inter-sample comparison of 14C dating using both gas counting (beta decay) and AMS dating techniques. We examine the adequacy of the standard gelatinization treatment for bone samples, which has been employed consistently at the laboratory since 1995.
    • Rudjer Bošković Institute Radiocarbon Measurements XIV

      Horvatinčić, Nada; Obelić, Bogomil; Krajcar Bronić, Ines; Srdoč, Dušan; Čalić, Romana (Department of Geosciences, The University of Arizona, 1999-01-01)
    • Use of Radiocarbon Dating in Assessing Christian Connections to the Dead Sea Scrolls

      Rodley, G. A.; Thiering, B. E. (Department of Geosciences, The University of Arizona, 1999-01-01)
      We present an analysis of radiocarbon dates on Dead Sea Scrolls that have a bearing on the question of the Scroll documents' relation to Christian origins. We assess details of dating reports, discuss paleographical evidence, and consider the content of the documents. When collated, these findings may be seen as compatible with a view that personalities mentioned in the Scrolls were contemporary with the founders of Christianity.