• Developments in the Calibration and Modeling of Radiocarbon Dates

      Ramsey, Christopher Bronk; Dee, Michael; Lee, Sharen; Nakagawa, Takeshi; Staff, Richard A. (Department of Geosciences, The University of Arizona, 2010-01-01)
      Calibration is a core element of radiocarbon dating and is undergoing rapid development on a number of different fronts. This is most obvious in the area of 14C archives suitable for calibration purposes, which are now demonstrating much greater coherence over the earlier age range of the technique. Of particular significance to this end is the development of purely terrestrial archives such as those from the Lake Suigetsu sedimentary profile and Kauri tree rings from New Zealand, in addition to the groundwater records from speleothems. Equally important, however, is the development of statistical tools that can be used with, and help develop, such calibration data. In the context of sedimentary deposition, age-depth modeling provides a very useful way to analyze series of measurements from cores, with or without the presence of additional varve information. New methods are under development, making use of model averaging, that generate more robust age models. In addition, all calibration requires a coherent approach to outliers, for both single samples and where entire data sets might be offset relative to the calibration curve. This paper looks at current developments in these areas.
    • Paleoearthquakes as Anchor Points in Bayesian Radiocarbon Deposition Models: A Case Study from the Dead Sea

      Kagan, Elisa J.; Stein, Mordechai; Agnon, Amotz; Ramsey, Christopher Bronk (Department of Geosciences, The University of Arizona, 2010-01-01)
      The Bayesian statistical method of the OxCal v 4.1 program is used to construct an age-depth model for a set of accelerator mass spectrometry (AMS) radiocarbon ages of organic debris collected from a late Holocene Dead Sea stratigraphic section (the Ein Feshkha Nature Reserve). The model is tested for a case where no prior earthquake information is applied and for a case where there is incorporation of known ages of 4 prominent historical earthquakes as chronological anchor points along the section. While the anchor-based model provided a tightly constrained age-depth regression, the "non-anchored" model still produces a correlation where most of the 68% or 95% age ranges of the 52 seismites can be correlated to historical earthquakes. This presents us with the opportunity for high-resolution paleoseismic analysis and comparison between various sites.