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Archaeomagnetic dating

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Archaeomagnetic dating is based on our current knowledge of the secular variation of the geomagnetic field in the past and on the property of baked and burned materials such as baked clays, carried at high temperatures, to acquire during their cooling a stable remanent magnetisation called thermoremanent magnetisation. For isotropic and homogeneous materials, the direction of this magnetisation is parallel to the ambient geomagnetic field and its intensity is proportional to the field intensity.

Methodology

  • Taking in archaeological sites of oriented samples from “in situ” baked and burned structures (kilns, fireplaces, etc.)
  • Measurement of the remanent magnetization acquired in a cryogenic 2G magnetometer
  • Removal of secondary, unstable remanent magnetization components and isolation of the stable remanent components by stepwise demagnetization
  • Dating: comparison of the mean direction of the stable magnetization obtained for the structure, with the standard curves of the secular variation of the direction of the field in the past

Example of an archaeomagnetic dating of the last firing of a mediaeval tile kiln, discovered near the church St Gertrude on the market place of Nivelles. The most probably age of the last heating-cooling cycle is 938 A.D. obtained by referring to the standard curves of the secular variation of the direction of the field during the last 3 kyr in Paris (Gallet et al., 2002).

Contact

Prof. Jozef Hus
Tel. : +32-(0)60 39 54 82
Fax : +32-(0)60 39 54 23
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Dr. Souad Ech-chakrouni
Tel. : +32-(0)60 39 54 81
Fax : +32-(0)60 39 54 23
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