What is Archaeomagnetism?

Philippe and Valerie taking samples from an archaeolgoical site in France

Philippe and Valerie taking archaeomagnetic samples from a Roman aged achaeological site in France

For regular readers of this blog, the term “archaeomagnetism” will have been seen a number of times, most frequently in posts by me or Andy Herries!

Archaeomagnetism is the study of burnt material found on archaeological sites. This can include everything from hearths, fireplaces and kilns through to tiles, bricks and pottery. Basically anything that has been subjected to heat at some point, either deliberately (e.g. the firing of a pot) or accidently (e.g. if a fire burns down a building, its foundations and walls become suitable for archaeomagnetic study as a consequence).

In certain parts of the world (for specific time periods), it is possible to date archaeological samples by comparing the declination, inclination and intensity values recorded in the archaeomagnetic samples (these 3 values describe the geomagnetic field vector) with the known changes in the geomagnetic field. One of the great things about archaeomagnetism (in my opinion) is the variety of ways in which you can use it. Associate Professor at Liverpool, Andy Herries, focuses on dating Hominid sites in South Africa by dating speolotherms (speolotherms are also known as flow stones and are created through the deposition of carbonate through time. Stalactites and stalagmites form in the same way.) see http://www.ncbi.nlm.nih.gov/pubmed/21392817.   It is worth noting that in speoltherms the record of the magnetic field is preserved as a chemical remanant magnetisation rather than a thermal remament magnetisation.

I myself am focused on trying to gather well-dated archeointensity data from Turkey for the dual purpose of enabling archaeomagnetic dating in the future as well as allowing us to accurately reconstruct changes in the geomagnetic field. This work is very interesting because there have been a number of recent papers linking sudden changes in the magnetic field with climate change and civilisation collapse e.g. http://www.sciencedirect.com/science/article/pii/S0012821X06002792.  I’m investigating whether I can see any evidence for this.

In this post I have only briefly mentioned some of the applications of archaeomagnetism: it is a fascinating field with new methods and ideas being tested every day.

About Megan Hammond

I am a final year PhD student based in the geomagnetism laboratory at the University of Liverpool. I am studying sharp changes in geomagnetic field intensity and the possible links between field intensity, climate change and the collapse of civilized societies. I am so far mostly focused on using the microwave system based at Liverpool to determine the palaeointensity of archaeological samples from Turkey. I am currently working on samples from the Alalakh archaeological site in the Hatay Province as well as some mud bricks from the Oylum archaeological site in the Kilis Plain. My project partly stems from recent controversial work of Gallet et al (2006) who suggested that sudden sharp rises in geomagnetic field intensity in the past caused climate changes and major upheavals. An archaeomagnetic jerk represents a period of intensity maxima coinciding with a sharp cusp in field direction. Although my PhD is in archaeomagnetism I am interested in many aspects of geology particularly chemical geology, metamorphic assemblages and palaeontology and graduated from the University of Edinburgh in 2010 with a Masters of Earth Science. In my spare time I play many sports including Ultimate Frisbee and I enjoy reading and socialising.
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5 Responses to What is Archaeomagnetism?

  1. Erkcan Ozcan says:

    This is really an interesting topic of research. Where in Turkey are you collecting your samples? Do you do measurements on site?

    • Megan_Thomas says:

      Thanks Erkcan! Sorry for the delayed reply.

      My samples come from the Hatay Province near the border with Syria and from the Mersin Province in Southern Turkey on the Mediterranean coast. I don’t do the measurements on site as I need an oven or a microwave to heat the samples. So once the samples are collected, I measure them in the ovens/ microwave here at Liverpool.

  2. Rimpy Kinger says:

    Its really very nice explanation.

  3. Arpita Santra says:

    Can you please tell me who has devised this technique for the very first time? And is it a relative dating method or absolute?

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