Palaeomagnetism of stalagmites (speleothems) in SW Japan

A palaeomagnetic study has been carried out on three stalagmites from two limestone caves in SW Japan. Remanent magnetizations of the stalagmite samples are weak, but stable enough to record the geomagnetic field. The results indicate an internal consistency between several time-equivalent samples drilled from the same stalagmite. A tentative correlation is suggested between palaeomagnetic data from two stalagmites collected from the same cave, and data from two different limestone caves. Combined curves of declination and inclination variations are constructed on the basis of this tentative correlation between the alternatingfield cleaned results from the three stalagmites. These variation curves can also be tentatively correlated with those deduced from archaeomagnetic studies in SW Japan. In consequence, the curves are believed to represent records of past geomagnetic secular variation. The tentative age of the oldest end of this secular variation curve can be estimated at about 15 OOO yr BP, based on the correlation with the archaeomagnetic results. A possible long period of westerly declination and steep inclination is recognized in the older part of the variation