STUDY OF HEATING HISTORY IN ARCHAEOLOGICAL MATERIALS -COOKING EVIDENCE, AFFECTED VOLCANIC DISASTER, ETC.

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We studied the heating properties of remanent magnetization in archaeological remains and/or archaeological samples to elucidate their heating histories. For this purpose, development of new experimental method was attempted. The method composed of the revised Thellier's method and the precise thermal demagnetization etc. utilizes the special qualities of thermoremanent magnetization in the heated samples.In Japan, there are several archaeological ruins affected by volcanic disaster, where the heating influence subjected by the volcanic deposits is the important information. At the ruin of Komochi-village in Gumma Prefecture completely damaged by the deposits from Mt.Haruna at the perid of ancient burial mounds, we studied through the developed method that the pumice-fall and the pyroclastic flow have reached at high temperature over 300 ℃, which supports the archaeologically suggested evidence. Also, the age of this volcanic disaster is determined by archaeomagnetic dating as the middle 6th century, which is concordant with the archaeological study.When the method was applied on the tiles used at the Mongolian Ogodai Palace (13th century) of Doityn-Balgas ruin, the sign of secondary heating was found. The direction of remanent magnetization suggests that the the has been used to construct the ceiling of the Palace. The estimated heated temperature of 150 ℃ studied by the Thellier's method indicates that the firing of the Palace may have occurred related with the war damage.The methods were also successfully applied on the other archaeological samples to investigate the reheated evidence and its age. We conclude that the heating parameter (temperature) innovated using the magnetic study becomes the important and useful information in archaeology.