Directional results and absolute archaeointensity determination by the classical Thellier and the multi-specimen DSC protocols for two kilns excavated at Osterietta, Italy
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We present a detailed rock-magnetic and archaeomagnetic study of two brick kilns, named OSA and OSB, discovered at the location of Osterietta, in northern Italy. The magnetic properties of representative samples have been investigated to identify the nature of the magnetic carriers, their domain state and thermal stability, and investigate their suitability for archaeomagnetic determinations. Thermally stable, mainly pseudosingle domain (PSD) magnetite is identified as the main magnetic carrier. The full geomagnetic field vector has been determined for the two kilns, including directional and intensity analysis. Archaeointensities have been recovered with both the classical Thellier and the multi-specimen protocols. The multi-specimen procedure was performed with a very fast-heating oven developed at Montpellier, France. A Matlab® code for anisotropy correction during the Thellier experiment is provided. The archaeointensity results obtained from both techniques for the OSA kiln are of high quality and in good mutual agreement. For the OSB kiln, Thellier results are characterized by large standard deviation and the multi-specimen (MSP) technique was not successful. The obtained full geomagnetic field vector (declination, inclination and intensity) has been used for the archaeomagnetic dating of the two structures suggesting that the OSA kiln was for the last time used between 1761?1841 A.D. and the OSB kiln between 1752?1831 A.D., at 95% probability. This study shows that intensity determinations do not restrict the dating results when referring to the last few centuries, as this period is characterized by very small intensity variations.
Keywordssecular variation geomagnetic field vector archaeomagnetic dating Italy
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