• Pushing the Limits of AMS Radiocarbon Dating with Improved Bayesian Data Analysis

      Palonen, V.; Tikkanen, P. (Department of Geosciences, The University of Arizona, 2007-01-01)
      We present an improved version of the continuous autoregressive (CAR) model, a Bayesian data analysis model for accelerator mass spectrometry (AMS). Measurement error is taken to be Poisson-distributed, improving the analysis for samples with only a few counts. This, in turn, enables pushing the limit of radiocarbon measurements to lower concentrations. On the computational side, machine drift is described with a vector of parameters, and hence the user can examine the probable shape of the trend. The model is compared to the conventional mean-based (MB) method, with simulated measurements representing a typical run of a modern AMS machine and a run with very old samples. In both comparisons, CAR has better precision, gives much more stable uncertainties, and is slightly more accurate. Finally, some results are given from Helsinki AMS measurements of background sample materials, with natural diamonds among them.
    • Radiocarbon Analysis Confirms the Annual Nature of Sagebrush Growth Rings

      Biondi, Franco; Strachan, Scotty J.; Mensing, Scott; Piovesan, Gianluca (Department of Geosciences, The University of Arizona, 2007-01-01)
      In the Great Basin of North America, big sagebrush (Artemisia tridentata Nutt.) growth rings can be used to reconstruct environmental changes with annual resolution in areas where there is otherwise little such information available. We tested the annual nature of big sagebrush wood layers using accelerator mass spectrometry (AMS) radiocarbon dating. Four cross-sections from 3 sagebrush plants were collected near Ely, Nevada, USA, and analyzed using dendrochronological methods. Ten 14C measurements were then used to trace the location of the 196-364 bomb spike. Although the number of rings on each section did not exceed 60, crossdating was possible within a section and between sections. Years assigned to individual wood layers by means of crossdating aligned with their expected 14C values, matching the location of the 14C peak. This result confirmed the annual nature of growth rings formed by big sagebrush, and will facilitate the development of spatially explicit, well-replicated proxy records of environmental change, such as wildfire regimes, in Great Basin valleys.
    • Radiocarbon Dating of Several Ancient Jewish Oil Lamps from Rome

      Rutgers, Leonard V.; van der Borg, Klaas; de Jong, Arie F. M. (Department of Geosciences, The University of Arizona, 2007-01-01)
      In this paper, we discuss how the radiocarbon dating of soot on oil lamps can help determine the chronology of the Jewish catacombs of Rome. We also explore the ramifications of our work for the typological study of Roman period terracotta lamps.
    • Radiocarbon Laboratories

      Department of Geosciences, The University of Arizona, 2007-01-01
    • Recurrence and Extent of Great Earthquakes in Southern Alaska During the Late Holocene from an Analysis of the Radiocarbon Record of Land-Level Change and Village Abandonment

      Hutchinson, Ian; Crowell, Aron L. (Department of Geosciences, The University of Arizona, 2007-01-01)
      The incidence of plate-boundary earthquakes across 3 prospective tectonic segments at the Alaska subduction zone (ASZ) in the late Holocene is reconstructed from geological evidence of abrupt land-level change and archaeological evidence of discontinuities in occupation of native villages. Bracketing radiocarbon ages on uplifted and down-dropped coastal deposits indicate that great earthquakes likely ruptured the plate interface in the eastern segment (Prince William Sound [PWS]) about 800, 1400, 2200-2300, 2600-2700, 3100-3200, and 3600-3700 cal BP. Evidence for an event about 1900 yr ago, and the possibility that the 26002700 cal BP event was a closely spaced series of 3 earthquakes, is restricted to parts of Cook Inlet. Geological evidence from the central (Kenai [KEN]) segment is fragmentary, but indicates that this segment likely ruptured about 1400 yr ago and in the triple event about 2600-2700 yr ago. The geological record from the Kodiak-Katmai (KOKA) segment at the western end of the ASZ has limited time-depth, with localized evidence for ruptures about 500, 1000, and 1300 yr ago. 14C ages and stratigraphic descriptions from 82 prehistoric villages and camps on the coast of the Gulf of Alaska reveal fluctuations in site activity that correlate with paleoseismic episodes. Hiatuses in site occupation occurred about 800, 1400, and 2200 yr ago in the PWS and KEN segments. The fragmentary older record from the KEN segment also reveals a hiatus about 2700 yr ago. The 2200-2300 and 2600-2700 cal BP events are also recorded in the KOKA segment, and the great earthquake at about 3200 cal BP may also be recorded there. This suggests that, although the PWS and KEN segments behave as a coherent unit of the Alaska megathrust, the KOKA segment is characterized by semi-independent behavior. At least 2, and perhaps as many as 4, of the last 7 prehistoric great earthquakes at this plate boundary did not propagate this far west.
    • Seoul National University Accelerator Mass Spectrometry (SNU-AMS) Radiocarbon Date List III

      Youn, M.; Song, Y. M.; Kang, J.; Kim, J. C.; Cheoun, M. K. (Department of Geosciences, The University of Arizona, 2007-01-01)
      The accelerator mass spectrometry (AMS) facility at Seoul National University (SNU-AMS) was accepted in December 1998 and results reported first at the Vienna AMS conference in October 1999 and at the 17th Radiocarbon Conference in Israel, June 2000. At the Vienna conference, we reported our accelerator system and sample preparation systems (Kim et al. 2000). Recent developments of the AMS facility have been regularly reported at AMS conferences (Kim et al. 2001, 2004, 2007). Meanwhile, about 1000 unknown archaeological, geological, and environmental samples have been measured every year. In this report, the archaeological and geological data carried out in 2001 are presented in terms of years BP (before present, AD 1950), following the SNU-AMS date lists I and II published in Radiocarbon (Kim et al. 2006a,b).
    • Seoul National University Accelerator Mass Spectrometry (SNU-AMS) Radiocarbon Date List IV

      Youn, M.; Song, Y. M.; Kang, J.; Kim, J. C.; Cheoun, M. K. (Department of Geosciences, The University of Arizona, 2007-01-01)
      The accelerator mass spectrometry (AMS) facility at Seoul National University (SNU-AMS) was accepted in December 1998 and results reported first at the Vienna AMS conference in October 1999 and at the 17th Radiocarbon Conference in Israel, June 2000. At the Vienna conference, we reported our accelerator system and sample preparation systems (Kim et al. 2000). Recent developments of the AMS facility have been regularly reported at AMS conferences (Kim et al. 2001, 2004, 2007). Meanwhile, about 1000 unknown archaeological, geological, and environmental samples have been measured every year. In this report, the archaeological and geological data carried out in 2002 are presented in terms of years BP (before present, AD 1950), following the SNU-AMS date lists I and II published in Radiocarbon (Kim et al. 2006a,b).
    • The Freshwater Reservoir and Radiocarbon Dates on Cooking Residues: Old Apparent Ages or a Single Outlier? Comments on Fischer and Heinemeier (2003)

      Hart, John P.; Lovis, William A. (Department of Geosciences, The University of Arizona, 2007-01-01)
      Fischer and Heinemeier (2003) present a hypothesis that the freshwater reservoir effect produces old apparent ages for radiocarbon dates run on charred cooking residues in regions where fossil carbon is present in groundwater. The hypothesis is based in part on their analysis of dates on charred cooking residues from 3 inland archaeological sites in Denmark in relation to contextual dates from those sites on other materials. A critical assessment of the dates from these sites suggests that rather than a pattern of old apparent dates, there is a single outlying datenot sufficient evidence on which to build a case for the freshwater reservoir effect.