The Ownership of Time: Approved [sup.14]C Calibration or Freedom of Choice?

By van Andel, Tjeerd H. | Antiquity, December 2005 | Go to article overview

The Ownership of Time: Approved [sup.14]C Calibration or Freedom of Choice?


van Andel, Tjeerd H., Antiquity


Radiocarbon analysis does not yield an age but a dimensionless ratio of two carbon isotopes, [.sup.12]C and [sup.14]C (Mook & van der Plicht 1999) which must be converted to an age in years by calibration. The simplest [sup.14]C-age calibration rests on the assumption that [sup.14]C has always been generated at a constant rate, thus making [sup.14]C years equal to calendar years. This assumption is not valid, however, because [sup.14]C years may deviate from calendar years by up to several thousand years, especially in the latest Pleistocene, and corrections are essential.

In 1996 the Godwin Institute of Quaternary Research of Cambridge University initiated a major interdisciplinary study called the (Oxygen Isotope) Stage 3 Project (van Andel 2003a). Based on existing data and new high-resolution palaeoclimate modelling, the project has placed Middle and Upper Palaeolithic human activity (60-20 ka BP) in a glacial climatic context. The detailed record of climatic change was derived from annual varves in Greenland ice-cores while archaeological sites provided proxies for human responses to climate changes that were largely [sup.14]C-dated. Calibration of [sup.14]C dates was thus critical to the project, but in the mid-1990s [sup.14]C calibration by the INTCAL group (Stuiver et al. 1998) had not advanced much beyond ~15 ka BP while the dataset to be calibrated extended back to c. 45 ka BE An interim calibration method was thus required to allow the project to proceed.

A serviceable approach for this purpose was proposed by Laurent Labeyrie (pets. comm. 1996). It rested on the time-variable intensity of the earth's magnetic field that controls the [sup.14]C production rate in the upper atmosphere (Mazaud et al. 1991). Using cores of marine and lake sediments and stacks of lava flows, Laj et al. (1996) calculated the changes in [sup.14]C production between ~20 and ~45 ka BP and derived a correction for [sup.14]C dates. For a while this method served the Stage 3 Project (van Andel 1998) well until in 1998 Joris and Weninger (1998, 2000a, 2000b) provided a superior high-resolution calibration method named 'CalPal'.

Today two principal paths exist for the conversion of [sup.14]C years into calendar years. One is the venerable method of direct comparison of a suite of [sup.14]C dates with a calendric chronology based on tree-rings, the paired-dates calibration mode (Stuiver et al. 1998). The Holocene [sup.14]C calibration is the principal example of this method; its extension into Pleistocene uses paired [sup.14]C and uranium/thorium dates (Taylor et al. 1996) and is now known as 'INTCAL' (Stuiver et al. 1998).

By the late 1990s the only attempt to calibrate Pleistocene [sup.14]C dates, the INTCAL project, using paired [sup.14]C and U/Th dates from corals, had not advanced beyond about 20 ka cal b.p. Also, its resolution was poor due to wide sample spacing, and progress was slow (Bard 2001; Bard et al. 1990, 1993, 1998; Stuiver et al. 1998). The latest 'official' calibration curve (INTCAL04), having reached 26 cal ka BE was recently ratified (Bard et al. 2004) and we are now eagerly awaiting INTCAL05. Had the Stage 3 group waited for completion of the INTCAL calibration project as instructed (van der Plicht 1999), many years would still have to pass before the Project, completed in 2003, could have proceeded.

The other mode is the stratigraphic path to calibration (Bard et al. 2004) of which CalPal is currently the principal version. Cores from the Greenland ice-cap contain a late Pleistocene history of rapid cold-warm climate changes dated by annual varves and known as the Dansgaard/Oeschger (D/O) oscillations (Dansgaard et al. 1993). Early CalPal experiments used the D/O record as a calibrant (an event series dated in calendar years and suitable for calibrating radiocarbon dates) for [sup.14]C-dated events in North Atlantic pelagic sediments (e.g. Volker et al. 1998), and the large Stage 3 Project databases containing the human and mammalian [sup. …

The rest of this article is only available to active members of Questia

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this article

This article has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this article

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited article

The Ownership of Time: Approved [sup.14]C Calibration or Freedom of Choice?
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.