REGIONAL DIFFERENCES OF ARCHEOMAGNETIC FIELD AND THEIR APPLICATION TO THE ARCHEOMAGNETIC AGE DATING

随着古地磁资料的积累，揭示出日本诸岛内古地磁场存在着相当大的区域差异。本研究的目的是对日本各地区的地磁年龄差异进行分类，建立日本各地区的标准古地磁变化曲线，为更准确地测定古地磁年龄数据做出贡献。本研究项目使我们能够获得北国地区和东海地区的标准古地磁变化曲线。前者的古-长期变化曲线为500年-1550年，后者(东海区)的古-长期变化曲线为900-1700年。我们获得了北海道和青森县的古地磁资料，这些县的古地磁结果较少。此外，我们还成功地获得了韩国的古地磁数据。这对于考证和厘清东亚地区古地磁场的分布及其长期变化将起到非常重要的作用。在与古代北陆地区的炼铁工业密切相关的炭窑上进行了地磁测量。研究表明，不仅奈良-平安和白松(江户时代末期)-明治时期，北国地区的铁生产在12-13世纪也是繁荣的。

As the archeomagnetic data have been accumulated, it is revealed that there are considerable regional differences in the ancient geomagnetic field within the islands of Japan. The differences are so big that ages obtained by the archeomagnetic dating show errors more than 100 years in the certain period.The aim of the present research is to clalify the regional differences and to establish the standard archeo-secular variation curve for each region in Japan to contribute to the more acculate archeomagnetic age dating.The present research project allowed us accomplishing the standard archeo-secular variation curves for the Hokuriku District and also for the Tokai District. The archeo-secular variation curve for the formar (Hokuriku District) is obtained for a period from 500 A.D.to 1550 A.D.and that for the latter (Tokai District) is for a period of 900-1700 A.D.We obtained archeomagnetic data from the Hokkaido and the Aomori Prefectures where scarce archeomagnetic results are reported. Moreover, we succeeded to obtain archeomagnetic data from Korea. Those will play a very important role to consider and clarify the distribution of the archeomagnetic field and its secular variation in the east Asia.Archeomagnetic measurements were carried out on charcoal kilns which had a close connection with the iron production industry in the ancient times in Hokuriku District. This study revealed that the iron production industies were prosperous not only in the Nara-Heian and the Bakumatsu (the end of Edo Era)-Meiji periods but also in the 12-13th Centuries in the Hokuriku region.