The Middle Miocene Daijima-type Floras in Southwestern Border of Northeast Honshu, Japan

Abstract

As shown in Fig. 1, the Middle Miocene Daijima-type floras are sporadically distributed in southwestern border of Northeast Honshu, Japan. Among them, the Kamigo flora of Tsuruoka, the Ikazuchi flora of Ikazuchi, the Okiniwa and the Oguni floras of Oguni were studied by the present authors. As listed in Table 3, 191 species which fall in 55 families and 123 genera were recognised from these four floras. It is suggested that these fossil plants were deribed to the sedimentary basins from the successive three forests such as the oak-laurel forest of lowland, the Comptonia-Liquidambar forest on adjacent slopes, and the temperate forest on surrounding mountains. The general physical condition under which these floras existed are supposed to be humid and warm to temperate climate in a region affected by a warm sea, as seen in the modern forests of Pacific coastal regions in southwestern Japan.