八戸浮石層直下の埋没土の植物珪酸体(プラントオパ-ル)分析

概要

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Plant opal analysis on the buried soil directly under the Hachinohe pumice bed distributed in the eastern foothill of the Towada Volcano was carried out. The time of the soil formation is about 13, 000 years B.P. (14C date), that is, late Glacial substage.The plant opal assembleages in the soil are characterized by plant opals originated from Gramineae such as the Festucoid, the Point and the Elongate types and those of coniferous trees such as Picea, Abies and Pinus. This means that the Gramineae plant was Poaceae, the dominant grass in the subarctic zone but Miscanthus sinensis (Panicoideae) and Zoysia japonica (Eragrostoideae) are dominant grasses at present in the surveyed area locating under the cool-temperate climate. Therefore, the climate indicated by the plant opal assemblages is considered to have been, cooler than the present one.