Ferromagnetic minerals in volcanic ash of the Osaka Group in Japan

Abstract

Plio-Pleistocene sediments of the Osaka, Kobiwako, and Tokai groups are among the most typical Quaternary sediments in Japan. The study of paleomagnetic chronostratigraphy of the volcanic ash embedded within these sediments was carried out by the present writer in collaboration with others [Ishida et al., 1969]. The results of this study show that the age of the paleoclimatological and paleontological episodes could be deduced from the correlation of its paleomagnetic data with the polarity time scale presented by Cox and Dalrymple [1967]. Lately, a method of identification of volcanic ash by thermomagnetic analysis was developed by Momose et al. [1968]. They carried out a series of thermomagnetic studies on ferromagnetic minerals taken from pumice-fall layers embedded within the Pleistocene tephra deposit, and reported that the thermomagnetic examination would be helpful for identification of pumice.