本州西部における第三紀型植物群の消滅について

抄録・要旨

Many pollen stratigraphy from Pliocene-Pleistocene sediments have been studied in Western Honshu，Japan. Recently stragraphy of the sediments in many area has been revised by correlation of volcanic ash layers. In this paper，pollen flora are examined in revised stratigraphy in the Uonuma Group and Tsunozu Group in Japan sea side，and Kazusa Group and Osaka Group in Pacific side. The period of disappearance of pollen grains of Pseudolarix. Keteleeria. Liquidambar and Metasequoia indicating Tertiary flora is indicated in these Groups. Therefore，the beginning of disappearance of Tertiary flora is probably Ordovai subchron in the Uonuma Group. The pollen grain of Tertiary flora disappeared in probably Pliocene-Pleistocene boundary for Tsunozu group, followed by Osaka Group, then middle Pleistocene in Kazusa Group. This designats possibility that Tertiary flora of Japan sea side disappeared ealiar than these of the Pacific side.13;