日本の鮮新-更新統の植物化石による分帯  [in Japanese] Plant biostratigraphy of the Plio-Pleistocene Series in Japan  [in Japanese]

The Pliocene-Pleistocene series, which abundantly contain plant fossils, are widely developed along the coastal plain and in the inland basin areas in Japan. Among these Japanese Pliocene-Pleistocene series, the Osaka Group in Osaka area, the upper part of Yamato Group in Aizu basin and the Uonuma Group in Niigata area are the most investigated in details. On the basis of magnetostratigraphical evidences and stratigraphical distribution of the main taxa of plants in these groups (Table 1), four regional zones are recognized, as shown in Table 2, namely, the Metasequoia-Glyptostrobus-Nyssa-, Metasequoia-Juglans cinerea var. megacinerea-Fagus microcarpa-, Metasequoia-Juglans mandshurica-Menyanthes trifoliata- and Fagus crenata-Juglans ailanthifolia-Tsuga diversifolia-Zones, in ascending order. Metasequoia-Juglans mandshurica-Menyanthes trifoliata-Zone is subdivided into two subzones, namely, the Juglans cinerea var. megacinerea-Pinus koraiensis- and Juglans mandshurica-Pinus koraiensis- Subzones. Fagus crenata-Juglans ailanthifolia-Tsuga diversfolia- Zone is, on the other hand, subdivided into two subzones, namely, the Lower and Upper subzones, though these subzones are not clearly recognized in the upper part of Uonuma Group. Metasequoia-Glyptostrobus-Nyssa-Zone and Metasequoia-Juglans cinerea var. megacinerea-Fagus microcarpa-Zone can be respectively assigned to be Early and Late Pliocene, and Metasequoia-Juglans mandshurica-Menyanthes trifoliata-Zone and Fagus crenata-Juglans ailanthifolia-Tsuga diversifolia-Zone are also respectively assigned to be the Early and Middle Pleistocene. The Nagano Formation in Kagoshima area and the Shimizumaebi Formation in Fukushima basin are included in the Metasequoia-Juglans cinerea var. megacinerea-Fagus microcarpa-Zone. The Kokubu Group in Kagoshima area, the Utatsuyama Formation in Kanazawa area, the Mandano Formation in Boso Peninsula and the Takada Formation in Fukushima basin are included in the Fagus crenata-Juglans ailanthfolia-Tsuga diversifolia-Zone. The upper part of Utatsuyama Formation, the Mandano Formation and the Takada Formation belong to the Upper Subzone of above mentoined zone. The Kokubu Group and the lower part of Utatsuyama Formation is to belong to the Lower Subzone of the zone. The Nitapporo and Otoebetsuga Formations in Ishikari lowland are included in the Fagus crenata-Juglans ailanthifolia-Tsuga diversifolia- Zone. The Simonopporo Formation in Ishikari lowland may be assigned to the Junglans mandshurica-Pinus koraiensis Subzone and the Lower Subzone of Fagus crenata-Juglans ailanthifolia-Tsuga diversifolia-Zone. At the boundary time between Metasequoia-Glyptostrobus-Nyssa-Zone and Metasequoia-Juglans cinerea-Fagus microcarpa-Zone, just before the Gauss/Matsuyama boundary, some Neogene elements of plants disappeared from the Japanese Islands. Moreover, at the boundary time between Metasequoia-Juglans mandshurica-Menyanthes) trifoliata-Zone and Fagus crenata-Juglans ailanthifolia-Tsuga diversfolia-Zone, just before the Matsuyama/Brunhes boundary, most of Neogene elements of plants disappeared from the Japanese Islands. The boreal elements of plants, such as Pinus koraiensis, Picea jezoensis, Menyonthes trifoliata and etc., widely distributed in the northern part of Chinese Continent and the higher mountains of Japanese Islands, appeared first after the Oldovai Subchron, which is assigned to the lower boundary of Metasequoia-Juglans mandshurica-Menyanthes trifoliata-Zone. Such endemic species distributed in the Japanese Islands as Fagus crenata, Juglans ailanthifolia, Pterocarya rhoifolia and Tsuga diversifolia are first appeared at the time, just before the Matsuyama/Brunhes boundary, that is the lower boundary of Fagus crenata-Juglans ailanthfolia-Tsuga diversifolia-Zone. On the basis of the stratigraphical changes of composition of the plant fossil assemblages, the present paper asserts that the geographic divergency of vegetation in the Japanese Islands became mo