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Archaeomagnetism |
Institute of Geophysics, Meteorology, and Space Physics, University of Alberta, Edmonton, Canada T6G 2J1
Palaeomagnetic methods were first applied to archaeological materials and very young geological formations in the Mediterranean region a century and a half ago. Although the pioneering work established the general validity of the method, the data remained sparse and permitted only limited conclusions. By the mid-1920s, thorough investigations of the lava flows of Mt. Etna demonstrated how geomagnetic secular variation could be traced back into pre-observatory epochs. In the following decade, systematic study of archaeological features commenced, but it was not until the 1960s that the database had grown to the point where useful geomagnetic inferences could be drawn. For the Mediterranean region, there are currently available two extensive data sets (one for France, the other for Bulgaria) containing a total of c. 400 directional results. For Italy and Greece, a useful start has been made (c. 100 results); for other countries (Morocco, Tunisia, Turkey) only a handful of results have been published. Collectively these data enable us to trace back the directional behaviour of the geomagnetic field with resonable confidence for the last 2000 years, but with less certainty for earlier times. Nevertheless, a picture is emerging in which static flux bundles and flux spots undergoing zonal retrograde drift can be recognized. Since the determination of geomagnetic field strength does not require in situ material, the investigator is freed of the need for accurately oriented samples and the scope of archaeomagnetic research is therefore enlarged. Many results have been published, but their status remains questionable due to the on-going debate concerning the validity of the different experimental procedures. Intensity and directional results have potential for archaeological dating both in an absolute and in a relative sense. Some authors claim the possibility of achieving a precision approaching ±50 years, but this depends strongly on the region and time interval in question. One example of particular interest is the application of archaeomagnetic data to the demise of the Minoan civilization.
