The early Pleistocene Tugm Tephra Bed in the Niigata region and the Kd18 Tephra Bed in the Boso Peninsula were correlated to the Ashino Pyroclastic Flow Deposit in the Aizu region. They contain bubble-junction type glass shards and high quartz in common. Chemical composition of glass shard and orthopyroxene (Mg#=63.6-66.0) of these tephra is also coincident. These tephras are expected to be found as marker beds in Japan.
The geochronologic units of Palaeogene and Neogene have long been described in Japanese as "Kodaisanki" and "Shindaisanki", which mean old and young Tertiary, respectively. The International Commission on Stratigraphy, however, recently proposes the revised geochronologic chart, demonstrating the subdivision of the Cenozoic Era into the Palaeogene and Neogene Periods instead of the Tertiary and Quaternary. The Japanese wording "Kodaisanki" and "Shindaisanki", therefore, should be reconsidered in terms of derivatio nominis of Palaeogene and Neogene. Here we review the Japanese usages of Palaeogene and Neogene in previous textbooks back to the end of the nineteenth century. It is concluded that the words "Koseiki", "Shiseiki" or "Kyuseiki" for Palaeogene and "Shinseiki" or "Kinseiki" for Neogene have already been proposed and described by Prof. Matajiro Yokoyama. These Japanese terms for Palaeogene and Neogene would be taken into consideration to write geological reports and papers in Japanese.