Daijima-type conifer wood assemblage of the Hatamura Formation (Mid-dle Miocene) in the Akita Prefecture, Japan

摘要

The paleofloral change from the Aniai-type to the Daijima-type during the Miocene is the most distinctive and rep-resentative one of the six floral changes in the Japanese Archipel-ago during the Tertiary. These floral types are based mainly on compressed or imprinted leaf fossils. In Korea, the transition-type between the Aniai- and Daijima-type floras has been proposed based on the fossil wood assemblages, and the Hatamura Forma-tion, which is the same age as the Daijima Formation, has yielded abundant fossil woods. To confirm whether the fossil wood assem-blages are in agreement with the paleofloras inferred from fossil leaves, the fossil woods from the Hatamura Formation were stud-ied. We found that warm temperate and daijiman elements, such as Keteleeria, Taxodimylon cunninghamioides, T sequoianum and Pinus, were present in the Hatamura Formation. Therefore, it can be concluded that the fossil wood types from the Hatamura For-mation agree well with the Daijima-type Flora. This result, in turn, verifies the existence of transitional flora between the Aniai-and Daijima-types in Northeastern Asia.