A paleomagnetic secular variation record of geomagnetic field direction for the time span from 25 to 16 ka was obtained from oriented bog sediment samples in a coastal area of the eastern Inland Sea, Japan. The plot of this secular variation record, combined with Holocene secular variation data, shows that a long-term westerly declination feature began after 16ka and ended at 7.5ka. This feature lasted more than 4,000 years and less than 8,500 years. The declinations at 25-16ka are dominated by easterly values, and no westerly declination was observed in the time span of 24-19.5ka. The inclinations at 25-16ka are characterized by slightly shallow values with small amplitude changes, compared to those in the Holocene. Prior to 18ka a large clockwise looping was dominant in the motion of the geomagnetic vector, while counterclockwise rotations were dominant after it. Many features of secular variation in the last glacial period have the potential to yield good age constraints for use in paleomagnetic dating.
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