Abstract
The Middle Pleistocene “hpm1” tephra layer of the Lowermost Daisen Tephra Formation has been found over the northern Kinki District. Examinations of the hornblende chemistry and the heavy mineral assemblage of the tephra revealed that Kumiyama volcanic ash layer and P5 or P6 volcanic ash layer can be correlated to “hpm1”, respectively. The results indicate that “hpm1” is potentially a widespread tephra and useful as a datum plane in the late Middle Pleistocene at ca. 230ka.
