Archaeomagnetic dating
Archaeomagnetic dating is the study and interpretation of the signatures of the
dating methodologies used for sites within the last 10,000 years.[1] The method was conceived by E. Thellier in the 1930s[2] and the increased sensitivity of SQUID magnetometers
has greatly promoted its use.
Instances of use
The
North Magnetic Pole and the local secular variation to yield a magnetic declination
.
The magnetic declination at any given time can be frozen into a clay formation that contains magnetite and is heated above the Curie point
. In general, many cultures used long-term fire hearths made of clay bricks, or a space lined with clay, that were baked into place by use. These artifacts of occupation can yield the magnetic declination from the last time they were fired or used.
Archaeomagnetic dating was described in the 1992 publication “Paleomagnetism: Magnetic Domains to Geologic Terranes.” By Robert F. Butler.[3]
Methodology
Archaeomagnetic dating requires an undisturbed feature that has a high likelihood of containing a remnant magnetic moment from the last time it had passed through the
tree ring dating or carbon-14
dates, help refine the regional curves.
Technique
A number of samples are removed from the feature by encasement in non-magnetic plaster within non-magnetic moulds. These samples are marked for true north at the time of collection. The samples are sent to an Archaeomagnetic Laboratory for processing. Each of the samples is measured in a spinner
eigenvector is generated that shows the three-dimensional magnetic declination
that will yield a location for the North Pole at the time of the last thermal event of the feature. Data from this feature is compared to the regional secular variation curve in order to determine the best-fit date range for the feature's last firing event.
See also
References
- ^ Eighmy, Jeffery; Sternberg, Robert (1990). "Archaeomagnetic Dating". Tucson: The University of Arizona Press.
- ^ Thellier E., 1938 Sur l’aimantation des terres cuites et ses applications geophysiques. Annales de l’Institut de Physique du Globe, 16, 157–302
- ^ Robert F. Butler (1992). "Paleomagnetism: Magnetic Domains to Geologic Terranes". Boston: Blackwell Scientific Publications. Archived from the original on 1999-02-18.
- Archaeomagnetic dating - guidelines, English Heritage booklet (p. 33), 2006 (a popular introduction with illustrations and references)
- Herries, A.I.R., Kovacheva, M., Kostadinova, M., Shaw, J., 2007. Archaeo-directional and -intensity data from burnt structures at the Thracian site of Halka Bunar (Bulgaria): The effect of magnetic mineralogy, temperature and atmosphere of heating in antiquity, Physics of the Earth and Planetary Interiors. 162, 199–216.
External links
- Archaeomagnetic Laboratory at the Illinois State Museum
- The U. S. National Geophysical Data Center (NGDC) data of paleopole positions and paleomagnetic directions.
- Yale University Archaeomagnetism Laboratory