Abstract
Plant opals in buried soils right below the Nanbu pumice layer (about 8, 600 years old, Oike and Takahashi, 1970) in the Nanbu area, Tohoku district, were separated and examined under the microscope. The constituents of plant opals in the buried soils gave the following informations on the vegetations of the Nanbu area in the early Holocene.
1) Plant opals were mostly originated from Gramineae, among which the Panicoid type (mostly produced by Paniceae) and the Sasaoid type (produced by so-called Sasa) dominate over the Festucoid type (produced by Poaceae). This means that the grass vegetation were constituted mostly of Paniceae and Sasa in the Nanbu area in the early Holocene.
2) Plant opals originated from trees, possibly Fagaceae and Magnoliaceae, were also found. However, their amount was far smaller than those from Gramineae.
