• A Random Walk Through Time

      Stuiver, Mitze (Department of Geosciences, The University of Arizona, 2009-01-01)
      A celebration is in order: the journal Radiocarbon is now a mature 50 years without drastic changes in its identity. There have been, of course, additions in terms of specific isotopes (it is now an international journal of cosmogenic isotope research), but the 14C content is still very extensive. The triannual offshoots, conference proceedings (started in 1980), and calibration issues (the first in 1986) testify to the strength of the 14C component. The following notes discuss a few historical aspects of my participation in the journal and its field of science. Some personal notes are also included. Advanced age (1% 14C decay would not be far off) is usually a good excuse for these wanderings.
    • Applications of Radiocarbon Dating Method

      Hajdas, Irka (Department of Geosciences, The University of Arizona, 2009-01-01)
      The main force driving technical development of the radiocarbon dating technique is the wide spectrum of applications that cross interdisciplinary boundaries of Earth and social sciences. This paper provides a very brief overview of some of the many applications of 14C analysis to various studies of human origin and migration, cultures and history, past and present environment, and the human body itself.
    • Archaeology Introduction

      Renfrew, Colin (Department of Geosciences, The University of Arizona, 2009-01-01)
    • Bayesian Analysis of Radiocarbon Dates

      Ramsey, Christopher Bronk (Department of Geosciences, The University of Arizona, 2009-01-01)
      If radiocarbon measurements are to be used at all for chronological purposes, we have to use statistical methods for calibration. The most widely used method of calibration can be seen as a simple application of Bayesian statistics, which uses both the information from the new measurement and information from the 14C calibration curve. In most dating applications, however, we have larger numbers of 14C measurements and we wish to relate those to events in the past. Bayesian statistics provides a coherent framework in which such analysis can be performed and is becoming a core element in many 14C dating projects. This article gives an overview of the main model components used in chronological analysis, their mathematical formulation, and examples of how such analyses can be performed using the latest version of the OxCal software (v4). Many such models can be put together, in a modular fashion, from simple elements, with defined constraints and groupings. In other cases, the commonly used "uniform phase" models might not be appropriate, and ramped, exponential, or normal distributions of events might be more useful. When considering analyses of these kinds, it is useful to be able run simulations on synthetic data. Methods for performing such tests are discussed here along with other methods of diagnosing possible problems with statistical models of this kind.
    • Calibration Commentary

      Blockley, S. P. E.; Housley, R. A. (Department of Geosciences, The University of Arizona, 2009-01-01)
      Radiocarbon is by far and away the most widely used dating tool in the Late Quaternary. Hundreds of key papers rely on the method to provide absolute and relative chronological information on important topics, including the late evolution of our own species (e.g. Higham et al. 2006a) and the timing and nature of abrupt climatic changes during the last glaciation (Lowe et al. 2001). Calibration of 14C determinations is an essential part of the dating process, and the implications of calibration can lead to significant differences in the interpretation of important processes (Blockley et al. 2006). Any development that enhances the accuracy, precision, or time coverage of the calibration curves is therefore to be welcomed. Since the early 1980s, there has been periodic publication of carefully vetted data in the form of internationally recognized consensus calibration curves that have allowed 14C users to convert their raw 14C determinations into calendar ages (Klein et al. 1982; Stuiver and Reimer 1986, 1993; Stuiver et al. 1998; Reimer et al. 2004). In the beginning, the basis on which this was done was easy to understand, 14C measurements were made on tree rings and the absolute calendar age came from counting annual growth rings. Although not without its complexities, the terrestrial tree-ring approach remains the most certain method and is at the heart of calibration process in the period 0-12.4 cal kyr. However, for periods beyond the limit of the tree-ring sequences the situation was significantly more problematic, and at times, even controversial.
    • Calibration Introduction

      Scott, E. M.; Reimer, P. J. (Department of Geosciences, The University of Arizona, 2009-01-01)
      There are 2 fundamental assumptions in radiocarbon dating, which were known early in the method development to be approximations, and which lead directly to the need to calibrate 14C dates: 1. The rate of formation of 14C in the upper atmosphere has been constant over the entire applied 14C dating timescale (approximately the last 65,000 yr). 2. The 14C activity of the atmosphere has been in equilibrium with the biosphere and ocean over the applied timescale.
    • Climatic Signature and Radiocarbon Chronology of Middle and Late Pleniglacial Loess from Eurasia: Comparison with the Marine and Greenland Records

      Haesaerts, P.; Borziac, I.; Chekha, V. P.; Chirica, V.; Damblon, F.; Drozdov, N. I.; Orlova, L. A.; Pirson, S.; van der Plicht, J. (Department of Geosciences, The University of Arizona, 2009-01-01)
      Recent investigations devoted to the Eurasian loess formations have provided an integrated high-resolution climatic sequence well radiocarbon dated between 13.4 and 42.5 kyr BP on charcoal and wood remains. Here, we show that the reproducible climatic signature of this loess sequence can be compared by proxy-correlation with the Greenland ice climatic signals, taking into account the distribution of the aeolian components in both records. This correlation allows situating with precision the series of 14C dates obtained from loess with regard to the Greenland climatic sequence. In this way, comparing the atmospheric loess-derived 14C chronology with the chronologies of the marine sequences becomes possible.
    • Dating Materials in Good Archaeological Contexts: The Next Challenge for Radiocarbon Analysis

      Boaretto, Elisabetta (Department of Geosciences, The University of Arizona, 2009-01-01)
      Radiocarbon dating has had an enormous impact on archaeology. Most of the dates are obtained using charred materials and, to a lesser extent, collagen from bones. The contexts in which charred materials and bones are found are often, however, not secure. There are 3 other datable materials that are usually in secure contexts: plaster/mortar, phytoliths, and the organic material in the ceramic of whole vessels. The plaster/mortar of walls and floors are often in very secure contexts. Phytoliths are abundant in archaeological sites and in some situations form well-defined surfaces. Whole vessels are usually found in secure contexts and their typologies are indicative of a specific period. Dating each of these materials has proved to be difficult, and solving these technical problems represents major future challenges for the 14C community. The effective use of charcoal and bone collagen for dating can also be improved by paying careful attention to the micro-contexts in which they are found, such as in clusters or as part of well-defined features. Pre-screening to identify the best preserved material can also contribute to improving the accuracy of the dates obtained. A general objective should be to have an assessment of the quality of the material to be dated so that the potentially invaluable information from outliers can be exploited.
    • Dendrochronology and Radiocarbon Dating: The Laboratory of Tree-Ring Research Connection

      Leavitt, Steven W.; Bannister, Bryant (Department of Geosciences, The University of Arizona, 2009-01-01)
      The field of dendrochronology had a developmental "head start" of at least several decades relative to the inception of radiocarbon dating in the late 1940s, but that evolution was sufficiently advanced so that unique capabilities of tree-ring science could assure success of the 14C enterprise. The Laboratory of Tree-Ring Research (LTRR) at the University of Arizona played a central role in the cross-pollination of these disciplines by providing the first wood samples of exactly known age for the early testing and establishment of the "Curve of Knowns" by Willard Libby. From the 1950s into the early 1980s, LTRR continued to contribute dated wood samples (bristlecone pine and other wood species) to 14C research and development, including the discovery and characterization of de Vries/Suess "wiggles," calibration of the 14C timescale, and a variety of tests to understand the natural variability of 14C and to refine sample treatment for maximum accuracy. The long and varied relationship of LTRR with 14C initiatives has continued with LTRR contributions to high-resolution studies through the 1990s and systematic efforts now underway that may eventually extend the bristlecone pine chronology back beyond its beginning 8836 yr ago as of 2009. This relationship has been mutualistic such that a half-century ago the visibility and stature of LTRR and dendrochronology were also elevated through their association with 14C-allied "hard sciences."
    • Development of Radiocarbon Dating in China Over the Past 50 Years

      Zhou, Weijian; Chen, Maobai (Department of Geosciences, The University of Arizona, 2009-01-01)
      On the arrival of the 50th anniversary of Radiocarbon, we review important developments in radiocarbon dating in China during the past 50 years, especially concerning 3 aspects: sample standard and preparation, accelerator mass spectrometry (AMS) facilities, and 14C applications. Specifically, these events are marked by the establishment of the Chinese sucrose charcoal standard in China; the development of small-sample dating in the Xi'an Laboratory of Loess and Quaternary Geology, Chinese Academy of Sciences (CAS); the progress of the AMS facilities in Beijing (China Institute of Atomic Energy and Beijing University); the innovation of the mini-cyclotron-based AMS at Shanghai Institute of Nuclear Research, CAS; the exploration of the Xia-Shang-Zhou chronology project in China; the establishment of the Xi'an multi-element AMS at the Xi'an-AMS Center; and the breakthrough in tracing the geomagnetic intensities and precipitation from 10Be in Chinese loess at the Institute of Earth Environment, CAS.
    • Developments in Radiocarbon Technologies: From the Libby Counter to Compound-Specific AMS Analyses

      Povinec, Pavel P.; Litherland, A. E.; von Reden, Karl F. (Department of Geosciences, The University of Arizona, 2009-01-01)
      We review developments in radiocarbon measuring techniques from the Libby counter through proportional gas counters and liquid scintillation spectrometers to the more recent developments of accelerator mass spectrometry (AMS), followed by a coupling of gas chromatography with AMS for compound-specific 14C analyses. While during the first 60 yr of 14C measurements beta counting, specifically gas counting, was the dominant technique, in the future of 14C science AMS will be the dominant technology.
    • Editorial Board

      Department of Geosciences, The University of Arizona, 2009-01-01
    • Modern and Pleistocene Reservoir Ages Inferred from South Pacific Corals

      Burr, G. S.; Beck, J. W.; Corrège, Thierry; Cabioch, G.; Taylor, F. W.; Donahue, D. J. (Department of Geosciences, The University of Arizona, 2009-01-01)
      This paper presents radiocarbon results from modern South Pacific corals from the Marquesas Islands, Vanuatu, Papua New Guinea (PNG), and Easter Island. All of the measurements are from pre-bomb Porites corals that lived during the 1940s and 1950s. The data reflect subannual to multiannual surface ocean 14C variability and allow for precise, unambiguous reservoir age determinations. The results are compared with published values from other coral records throughout the South Pacific, with striking consistency. By comparisons with other published values, we identify 3 South Pacific regions with uniform pre-bomb reservoir ages (1945 to 1955). These are 1) the Central Equatorial South Pacific (361.6 +/- 8.2 14C yr, 2 sigma); 2) the Western Equatorial South Pacific (322.1 +/- 8.6 14C yr, 2 sigma); and 3) the subtropical Pacific (266.8 +/- 13.8 14C yr, 2 sigma). The question of how much, and how fast, South Pacific reservoir ages might have varied in the past is addressed by examining a published record from a Pleistocene coral from Vanuatu that lived over a 700-yr period during the Younger Dryas. The average reservoir age at that time was larger than today, by ~150 yr, and exhibited reservoir age variability on a decadal timescale not seen in modern times. Measured paleo-reservoir ages increase sharply in this record by as many as 300 14C yr in 3 decades. These increases are punctuated by smaller reservoir age decreases, on the order of 150 yr. This reservoir age variability provides a rare picture of active ocean ventilation and ocean-atmosphere exchange at the close of the Pleistocene.
    • New Radiocarbon Dates and a Review of the Chronology of Prehistoric Populations from the Minusinsk Basin, Southern Siberia, Russia

      Svyatko, Svetlana V.; Mallory, James P.; Murphy, Eileen M.; Polyakov, Andrey V.; Reimer, Paula J.; Schulting, Rick J. (Department of Geosciences, The University of Arizona, 2009-01-01)
      The results are presented of a new program of radiocarbon dating undertaken on 88 human skeletons. The individuals derived from Eneolithic to Early Iron Age sites--Afanasievo, Okunevo, Andronovo (Fedorovo), Karasuk, and Tagar cultures--in the Minusinsk Basin of Southern Siberia. All the new dates have been acquired from human bone, which is in contrast to some of the previous dates for this region obtained from wood and thus possibly unreliable due to old-wood effects or re-use of the timber. The new data are compared with the existing 14C chronology for the region, thereby enabling a clearer understanding to be gained concerning the chronology of these cultures and their place within the prehistory of the Eurasian steppes.
    • Preface from the Editor

      Department of Geosciences, The University of Arizona, 2009-01-01
    • Radiocarbon and the Old World Archaeology: Shaping a Chronological Framework

      Kuzmin, Yaroslav V. (Department of Geosciences, The University of Arizona, 2009-01-01)
      The inception of the radiocarbon dating method in 1949 was immediately supported by many archaeologists. In the following 2 decades, many important archaeological sites in the Old World were dated, marking the beginning of building a reliable chronological framework for prehistoric and early historic cultural complexes worldwide. The author presents an observation of some of the most important results in establishing a chronology for Old World archaeology, based on 14C dating performed in the last 50 yr. An extensive bibliography should help scholars to get acquainted with early summaries on archaeological chronologies based on 14C data and their evaluation, as well as with some recent examples of the application of 14C dating in Old World archaeology.
    • Radiocarbon Dating History: Early Days, Questions, and Problems Met

      Olsson, Ingrid U. (Department of Geosciences, The University of Arizona, 2009-01-01)
      W F Libby's new dating method from the 1940s, based on experience in physics and chemistry, opened possibilities to check and revise chronologies built on other principles than radioactive decay. Libby's method initially implied collaboration with archaeologists to demonstrate that it worked but also with physicists to improve the technique to measure low Beta activities. Chemists, geophysicists, botanists, physiologists, statisticians, and other researchers have contributed to a prosperous interdisciplinary development. Some pitfalls were not recognized from the beginning, although issues such as contamination problems were foreseen by Libby. Pretreatment of samples was discussed very early by de Vries and collaborators, among others. This subject has not yet been abandoned. Closely related to pretreatment is the choice of fraction to be dated and chemicals to be used, especially for accelerator mass spectrometry (AMS) measurements. Calibration against tree rings and comparison with dates obtained using other methods as well as intercomparison projects are partly history but still very actual. The impact by man and climate is also studied since the early days of the method. Also, the carbon cycle has been of great interest. The tools for measurements and statistical analysis have been improved during these first 3 or 4 decades, allowing interpretations not possible earlier. 13C determinations are mostly very important and useful, but sometimes they have been misleading in discussions of the origin of carbon, especially for human tissues--the metabolism was not yet fully understood. The history and development of the method can only be illustrated by selected examples in a survey like this.
    • Rolling Out Revolution: Using Radiocarbon Dating in Archaeology

      Bayliss, Alex (Department of Geosciences, The University of Arizona, 2009-01-01)
      Sixty years ago, the advent of radiocarbon dating rewrote archaeological chronologies around the world. Forty years ago, the advent of calibration signaled the death knell of the diffusionism that had been the mainstay of archaeological thought for a century. Since then, the revolution has continued, as the extent of calibration has been extended ever further back and as the range of material that can be dated has been expanded. Now a new revolution beckons, one that could allow archaeology to engage in historical debate and usher in an entirely new kind of (pre)history. This paper focuses on more than a decade of experience in utilizing Bayesian approaches routinely for the interpretation of 14C dates in English archaeology, discussing both the practicalities of implementing these methods and their potential for changing archaeological thinking.
    • Six Decades of Radiocarbon Dating in New World Archaeology

      Taylor, R. E. (Department of Geosciences, The University of Arizona, 2009-01-01)
      Radiocarbon (14C) dating provided New World archaeological research with the first continent-wide common chronometric scale that transcended the mostly relative site- and region-specific chronological sequences that had been assembled during the preceding century of fieldwork. 14C data continue to play a critical role in establishing a chronometric framework for the 5-century-long debate concerning the timing of the initial peopling of the New World. Other issues where 14C results have been of particular importance include the origins and development of New World agriculture and determination of the relationship between the Western and Classic Maya long-count calendar. The introduction of a third-generation measurement technology of accelerator mass spectrometry (AMS) beginning in the late 1970s has provided a means of obtaining analyses on milligram and microgram amounts of carbon permitting more detailed critical approaches to increasing the accuracy of 14C values on certain sample types--particularly human skeletal materials. It also provided a more effective means of allowing greater dating precision in situations where such data had an important bearing on the validity of inferences about the rates of cultural evolutionary change in New World societies.
    • Table of Contents

      Department of Geosciences, The University of Arizona, 2009-01-01