東北本州弧南部における中〜下部中新統の植物化石層位について  [in Japanese] On the plant biostratigraphy of the Middle to Lower Miocene strata in the southern part of Northeast Honshu Arc, Japan  [in Japanese]

The writer examined the characters of the composition and the stratigraphical distribution of the plant fossil assemblages from the Middle to Lower Miocene strata in the southern part of Northeast Honshu Arc, Japan. As a result, those fossil assemblages could be divided into the three biostratigraphic units; the Aniai type flora, Aniai-Daishima mixed type flora and Daishima type flora in ascending order. The Aniai type flora consists of the taxonomic groups found only in the deciduous broad-leaved forest distributing in the temperate region, as already described by HUZIOKA (1964, 1974). The Daishima type flora consists of the taxonomic groups found in the evergreen and deciduous broad-leaved orests distributing in the warm temperate to subtropical regions, as already described by HUZIOKA (1973). The Aniai-Daishima mixed type flora, which is proposed in the present paper, consists of the mixture of taxonomic groups found only in the deciduous broad-leaved forest in the temperate region and those found in the evergreen and deciduous broad-leaved forests in the warm temperate to subtropical regions. The first appearance of the Aniai-Daishima mixed type flora is considered to be correspondent with the time of lowest limit of Actinocyclus ingens zone or the time of Kisseleviella carina zone in the Joban area of Pacific coastal region. The first appearance of the Daishima type flora is considered to be correspondent with the period in the N8 zone of planktonic foraminiferal zones in the southern part of Northeast Honshu Arc.